This has been CNBC's live blog covering updates on the war in Ukraine. [Follow the latest updates here.]

Ukraine's President Volodymyr Zelenskyy on Wednesday pushed companies that that have not shut down operations in Russia to leave the country and instead set up in Ukraine.

Speaking to U.S. business leaders at the Yale CEO summit, he also warned of widespread famine if Russia does not lift a blockade of Ukrainian ports that has prevented the export of grains.

Late Tuesday night, Zelenskyy warned that this coming winter will be "the most difficult" for Ukraine since its independence from the Soviet Union. He said the country won't sell gas and coal abroad.

Meanwhile, a report suggested that more than 1,000 Ukrainian fighters captured in Mariupol have been sent to Russia for an "investigation." There have been widespread concerns over the fate of soldiers captured in the southern port city after Russia seized it in late May.

UN chief says trade deal could avert mass hunger

The United Nations is pursuing a deal that would allow grain exports from Ukraine through the Black Sea and unimpeded access to world markets for Russian food and fertilizers.

Secretary-General Antonio Guterres told U.N. correspondents on Wednesday that without the deal hundreds of millions of people in developing countries face the threat of an unprecedented wave of hunger, three months after Russia invaded its smaller neighbor.

Guterres said, "Ukraine's food production and the food and fertilizer produced by Russia must be brought into world markets, despite the war."

Senior officials have been working closely with contacts in Moscow, Kyiv, Ankara, Brussels and Washington for the past 10 days, Guterres said. He said he didn't want to jeopardize the chances of success by revealing details.

"This is one of those moments when silent diplomacy is necessary, and the welfare of millions of people around the world could depend on it," he said.

— Associated Press

Biden reaffirms U.S. support in phone call with Polish president

President Joe Biden spoke with Polish President Andrzej Duda and reaffirmed U.S. commitment to bolster security along Poland's borders, the White House said in a readout of the call.

"They also discussed their ongoing support for the people and government of Ukraine in response to Russian aggression," the readout said.

Biden last met with Duda in March during a high-profile trip to Poland.

— Amanda Macias

Ukraine might be about to pull back from a key eastern city

Ukrainian troops may soon have to retreat from a key eastern city, the region's governor and Western military analysts said Wednesday, as Russian advances force them back.

The street-by-street battle for Sievierodonetsk has become the focus of the conflict in recent weeks, with Russia slowly advancing toward its larger goal to take full control of the industrial Donbas region.

The last major city still under Ukrainian control in the Luhansk province — which together with neighboring Donetsk makes up the Donbas — has been pummeled by artillery in a back-and-forth fight that remains hard to decipher. Kyiv said a counteroffensive over the weekend had helped its forces regain some ground, but the situation appears to have deteriorated further since then.

Satellite imagery released by U.S. defense contractor Maxar Technologies on Wednesday appeared to show what it said was "significant damage" in Sievierodonetsk and nearby areas amid fears that the city could be turned into a new Mariupol, the key port that was besieged by the Russians and left in ruins by relentless fighting.

Read more here.

— NBC News

Workers demine Ukraine's Chernihiv region

Ukrainian bomb disposal workers load unexploded ordnance in containers before transportation aboard a special vehicle during mine clearance work in the village of Yahidne, in the liberated territories of the Chernihiv region.

— Sergei Supinsky | AFP | Getty Images

Russian economy to shrink 15% this year, finance group says

Hard hit by sanctions since the Feb. 24 invasion of Ukraine, Russia's economy will shrink by 15% this year and another 3% in 2023, wiping out 15 years of economic gains, according to the Institute of International Finance, a global banking trade group.

The resilience of the ruble — Russia's currency — has partially shielded its economy from the full impact of sanctions. Propping up the ruble are strong oil and natural gas sales and the Russian central bank, which has raised interest rates and imposed capital controls to keep money from fleeing the country.

President Vladimir Putin said this week that unemployment and inflation are decreasing, backing up his frequent claims that Russia is succeeding despite Western sanctions.

Still, the finance institute argued that the sanctions, partly by encouraging foreign companies to abandon Russia, "are unraveling its economy, wiping out more than a decade of economic growth, and some of the most meaningful consequences have yet to be felt."

— Associated Press

Residents in Kharkiv help clean up destroyed shopping mall

Residents of Kharkiv help to clean up a destroyed shopping mall.

— Anadolu Agency

Arctic Council to resume work without Russia

The other seven governments that make up the Arctic Council said the group will resume work without Russia.

"We intend to implement a limited resumption of our work in the Arctic Council, in projects that do not involve the participation of the Russian Federation," the governments of Canada, Denmark, Finland, Iceland, Norway, Sweden, and the United States wrote in a joint statement.

The Arctic Council announced a pause in its work on March 3 following Russia's invasion of Ukraine.

— Amanda Macias

UN says at least 4,266 killed in Ukraine since start of war

The United Nations has confirmed 4,266 civilian deaths and 5,178 injuries in Ukraine since Russia invaded its ex-Soviet neighbor on Feb. 24.

The Office of the U.N. High Commissioner for Human Rights said the death toll in Ukraine is likely higher, because the armed conflict can delay fatality reports.

The international organization said most of the civilian casualties recorded were caused by the use of explosive weapons with a wide impact area, including shelling from heavy artillery and multiple launch rocket systems, as well as missiles and airstrikes.

— Amanda Macias

Zelenskyy says Russia is creating a 'food genocide worldwide' with port blockade

Ukrainian President Volodymyr Zelenskyy warned that Russia's occupation and blockade of Ukrainian ports in the Black Sea will cause a "food genocide worldwide."

"We have 20 billion worth of grains that have been blocked in Ukrainian ports," Zelenskyy said via video conference at the Yale CEO summit.

"We are going to have an additional 50 billion tons of grains and foodstuffs in Ukraine, which are going to be stranded in Ukraine because of the occupation and the blockage," he added.

For weeks, Russian forces have blocked roughly a dozen Ukrainian ports in the Black Sea and Sea of Azov.

— Amanda Macias

Zelenskyy asks U.S. corporate leaders to leave Russia and move to Ukraine

Ukrainian President Volodymyr Zelenskyy called on all remaining companies in Russia to leave the country and instead set up operations in Ukraine.

"I'd like companies to consider not only the option of leaving Russia but also finding their place in the Ukrainian economy," Zelenskyy told U.S. business leaders via video conference at the Yale CEO summit.

"This would be a powerful sign of support," he added.

Zelenskyy also called on company CEOs to not pay Russian taxes "because this money is used to finance Russia's war machine."

"Russia has violated international laws and our sovereignty," Zelenskyy said. He added that "it does not abide by laws of businesses, which means that they're going to dictate their own terms to you as well. Can you really do business with Russia now?"

— Amanda Macias

Occupied part of Zaporizhzhia reportedly set to have referendum on joining Russia

The Russian-occupied part of Ukraine's Zaporizhzhia region is set to have a referendum on joining Russia some time this year, Russian news agencies have reported, quoting an official within the military-civilian administration of the region.

"The people will determine the future of the Zaporozhzhia region. A referendum is scheduled for this year," Vladimir Rogov was reported as saying, according to news agency Tass.

According to Rogov, the referendum will be valid with a turnout of 50%. "The basis for holding a referendum is a guarantee of security in the territory," Rogov claimed.

Approximately 60% of the Zaporizhzhia region is under Russian control, according to Reuters, although the region's main city of Zaporizhzhia is still held by Ukraine. Nonetheless, a swathe of the southern Ukrainian region was seized early in the war, including most of the neighboring Kherson province.

There too, Russian-installed officials have planned to hold a referendum on becoming a part of Russia, a move widely seen as a bid by Moscow to lend legitimacy to its invasion and occupation of Ukraine.

For its part, Ukraine has said any referendums held under Russian occupation would be illegal.

— Holly Ellyatt

President Zelenskyy set to address CEOs at Yale summit

President Zelenskyy of Ukraine is joining the Yale CEO Summit for an interactive session that will stream only on CNBC.com at 9 a.m. ET.

CNBC Closing Bell Anchor Sara Eisen is in the room with Yale's Jeffrey Sonnenfeld and CEOs to speak directly with Zelenskyy.

Attendees are global leaders in business, politics and philanthropy and include Carlyle non-exec Co-Chairman David Rubenstein, Citigroup CEO Jane Frazer, Pfizer CEO Albert Bourla and IBM CEO Arvind Krishna as well as Liberty Media CEO Greg Maffei, Alcoa CEO Klaus Kleinfeld and Jared Kushner.

— Holly Ellyatt

Zelenskyy and Scholz discuss global food security

Ukraine's President Volodymyr Zelenskyy has discussed the latest developments in the war with his German counterpart, Olaf Scholz.

In a post on Twitter Wednesday, Zelenskyy said the leaders had "discussed enhancing defense support for and ensuring global food security."

He said he had also raised the issue of Russia's compliance with international rules regarding the treatment of prisoners of war, as well as matters regarding Ukraine's aspirations to join the EU.

— Holly Ellyatt

Russia's Lavrov says Ukraine has to de-mine ports to enable grain exports

Russian Foreign Minister Sergei Lavrov said issues relating to grain shipments from ports in Ukraine can be resolved, Reuters reported, provided that Kyiv de-mines the waters around them.

He added that Moscow would not use the situation surrounding grain shipments in and around the Black Sea to advance its "special military operation," as long as Ukraine lets ships leave safely.

"These are guarantees from the president of Russia," the news agency reported reported Lavrov as saying.

Speaking alongside his Turkish counterpart Mevlut Cavusoglu during a visit to the capital Ankara, Lavrov said Russia's invasion, or what it calls its "special military operation" in Ukraine, was going according to plan.

He added that peace talks would need to resume before there was any chance of presidential talks between President Vladimir Putin and Ukraine's President Volodymyr Zelenskyy.

— Reuters

Norway donates 22 howitzers to Ukraine

Norway has donated 22 M109 self-propelled howitzers to Ukraine as well as spare parts, ammunition and other gear, the Norwegian Defense Ministry said on Wednesday.

"The Norwegian Army has recently replaced their M109 artillery guns with new artillery from South Korea, but still has M109 stored. 22 of these have been donated, along with gear, spare parts and ammunition. Norway has also trained Ukrainian soldiers on how to use the system. This training has taken place in Germany," the ministry said in a statement.

Ukraine had specifically requested this type of weapon and recent developments in the war in Ukraine "now suggests that it is necessary to also donate heavier artillery and weapons' systems," Norwegian Defense Minister Bjorn Arild Gram commented.

The artillery pieces have been shipped from Norway, the ministry said, adding that the government had waited to publicly announce the donation for security reasons. Future donations may not be announced or commented upon, it added.

— Holly Ellyatt

Big stumbling blocks to Ukraine becoming a member of the EU

The European Union could be about to throw its support behind Ukraine becoming its newest member, but the process will not be easy.

Two main factors mean that Kyiv might have several years to wait before officially joining the political bloc.

A number of nations in the Western Balkans have already been promised EU membership — but negotiations have yet to begin. This is the case of North Macedonia, for instance.

One risk for the EU is that it is seen to be giving preferential treatment to Kyiv — upsetting other parts of the continent and potentially pushing them closer to Russia.

In addition, political analysts think that without a peace agreement with Russia, Ukraine will struggle to become a member of the EU.

Read more here: Ukraine wants to join the European Union. But it is not going to be easy

— Silvia Amaro

The fight in Donbas is tight, with neither side gaining much ground, UK says

Fierce fighting in eastern Ukraine has continued into this week, with Russian forces pounding the city of Severodonetsk and surrounding areas while Ukraine seeks to hold ground to avoid conceding more of the contested region to Russia.

In the last 24 hours, it's unlikely that either side has gained significant ground, according to Britain's Ministry of Defense.

"Russia continues to attempt assaults against the Sieverodonetsk pocket from three directions although Ukrainian defences are holding," the ministry said on Twitter on Wednesday. The intelligence update noted that while Russia is concentrating its offensive in the central Donbas sector, it has remained on the defensive on its flanks.

Elsewhere, the ministry said Ukrainian forces have recently achieved some success by counter-attacking in the southwestern Kherson region, including regaining a foothold on the eastern bank of the Ingulets River.

Nonetheless, "with the frontage of the occupied zone stretching for over 500km, both Russia and Ukraine face similar challenges in maintaining a defensive line while freeing up capable combat units for offensive operations," the U.K. said.

— Holly Ellyatt

Sweden and Finland want to join NATO. Here's how that would work

Members of the North Atlantic Treaty Organization (NATO) are due to meet later this month for a landmark summit in Madrid, Spain.

The recent requests from Finland and Sweden to join the alliance will be high in the agenda, particularly after Turkey raised concerns about allowing these new members in.

But how does a country join NATO and what does this mean for the rest of the world? CNBC takes a look at the process and what Stockholm and Helsinki have to offer to the  defense alliance.

— Silvia Amaro

More than 1,000 Mariupol fighters have been sent to Russia, report suggests

More than 1,000 Ukrainian soldiers who were captured after the fall of the southern port city Mariupol to Russian forces have been transferred to Russia for "investigation," according to Russian state news agency Tass.

Citing a Russian law enforcement source, Tass reported Tuesday that more Ukrainian prisoners are expected to be transferred to Russia in the near future.

"More than 1,000 people from Azovstal have been transferred to Russia. Law enforcement agencies are working closely with them. In the near future, after face-to-face confrontations with a number of prisoners of war, the investigation also plans to send them to Russia," the source said.

Tass did not have official comments from the investigating authorities and law enforcement agencies in its report and CNBC was unable to immediately verify the information.

There have been widespread concerns about the fate and treatment of hundreds of Ukrainian fighters captured (Russia says they surrendered) following the siege of Mariupol, and particularly the siege of the Azovstal steelworks in the city.

The steelworks became the last stronghold for hundreds of Ukrainian soldiers and civilians who were holed up within the complex for several months before Russian forces eventually seized the works.

Hundreds of Ukrainian fighters and civilians had been taken to a prison camp in Russian-controlled territory in Ukraine following the siege.

— Holly Ellyatt

Coming winter will be 'the most difficult' since independence, Zelenskyy warns

Ukraine's President Volodymyr Zelenskyy has said the government and energy companies have met to prepare energy provision for the coming winter, which he said would be the most difficult one for the country since its independence following the collapse of the Soviet Union in 1991.

"Whatever the occupiers plan for themselves, we must prepare for the next winter — in our state, on our land, for all citizens," he said in his nightly address Tuesday evening, adding that the purchasing of a sufficient amount of gas for the heating season, coal accumulation, and electricity production were discussed by Ukrainian ministries and energy companies.

"In the current situation due to Russia's aggression, this will indeed be the most difficult winter of all the years of independence," Zelenskyy said.

The president added that "at this time, we will not be selling our gas and coal abroad. All domestic production will be directed to the internal needs of our citizens.

At the same time, Zelenskyy said, Ukraine is doing what it can to increase its electricity export capabilities.

— Holly Ellyatt

Ukrainian officials say Mariupol might be facing a deadly cholera outbreak

The besieged Ukrainian city of Mariupol could now be facing a deadly cholera outbreak, NBC News reported, citing local officials.

Drinking water in the city has been contaminated by decomposing garbage and corpses, increasing the risk of a cholera outbreak, NBC reported, citing an advisor to the occupied city's mayor.

The advisor, Petro Andryushchenko, also added that a nearby Russian city across the border was preparing infectious disease units in case a cholera outbreak might affect Russian soldiers in Mariupol, NBC News reported.

"So really, this threat is not only recognized by the World Health Organization and us, but the occupants as well," Andryushchenko said on Ukrainian television, according to NBC News.

He said in a different interview that Russian authorities controlling Mariupol were effectively shutting down the city and imposing a self-imposed quarantine.

NBC News and CNBC could not independently confirm Andryushchenko's claim.

Cholera can kill within hours if left untreated, according to the WHO.

The organization last month warned of the threat of infectious disease outbreaks in Mariupol, citing local nongovernmental organizations that the city's sewage and drinking water were getting mixed, creating "a huge hazard for many infections, including cholera."

— Chelsea Ong

Germany's Merkel defends her approach to Ukraine

Angela Merkel defended her approach to Ukraine and Russia during her 16 years as Germany's leader, saying that a much criticized 2015 peace deal for eastern Ukraine bought Kyiv precious time and she won't apologize for her diplomatic efforts.

In her first substantial comments since leaving office six months ago, Merkel said there was "no excuse" for Russia's "brutal" attack on Ukraine and it was "a big mistake on Russia's part."

Merkel, who dealt with Russian President Vladimir Putin throughout her chancellorship, rejected a suggestion that she and others engaged in appeasement that ultimately enabled the invasion.

"I tried to work toward calamity being averted, and diplomacy was not wrong if it doesn't succeed," she said in an on-stage interview at a Berlin theater that was televised live. "I don't see that I should say now that it was wrong, and so I won't apologize."

"It is a matter of great sorrow that it didn't succeed, but I don't blame myself now for trying," Merkel said.

— Associated Press

Russian forces control 97% of Luhansk, defense minister says

Russian forces now control 97% of Ukraine's Luhansk region, Russian Defense Minister Sergei Shoigu said, according to the Associated Press.

The assessment comes after weeks of brutal fighting and heavy Russian artillery bombardment of much of the eastern Donbas, of which Luhansk is a part. Moscow says that full control over the Donbas is an "unconditional priority."

Much of the fiercest fighting, including street battles, is currently taking place in Luhansk in the cities of Sievierodonetsk and Lysychansk, where Russian forces have won major ground despite some recent successful efforts by Ukrainian troops to claw back territory.

Some officials and pundits in other countries have suggested Ukraine should give up the Donbas to Russia in exchange for peace, an idea Ukraine fiercely rejects. Kyiv and many of its Western allies warn that if they give up land to Russia, Moscow will only be incentivized to expand its gains and try to capture more Ukrainian territory. Russia has been ambiguous on whether it would seek to capture more land.

— Natasha Turak

World Bank slashes global growth forecast, says Russian invasion of Ukraine worsened economic slowdown

The World Bank cut its projection for global growth by 1.2 percentage points to 2.9% for this year, citing Russia's invasion of Ukraine as a further blow that was worsening an already hard-hit economy still recovering from the Covid pandemic and facing mounting inflation.

The world is entering a "protracted period of feeble growth and elevated inflation," the organization wrote in its latest Global Economic Prospects report.

Russia's war in Ukraine has slammed global food exports, particularly grains and cooking oils — a huge proportion of which are exported by the two warring countries — because Russian forces are blocking Ukraine's vital Black Sea ports.

The disruption in agricultural supplies has hit Middle Eastern and African economies particularly hard, as these regions rely heavily on Black Sea food exports and their largely lower-income populations are now struggling under acute food price inflation.

"With inflation now running at multi-decade highs in many countries and supply expected to grow slowly, there is a risk that inflation will remain higher for longer," World Bank President David Malpass wrote.

The World Bank expects global growth to slow by 2.7 percentage points between 2021 and 2024. Global growth had reached around 5.5% in 2021, the Bank wrote previously.

— Natasha Turak