• Russian forces have struck a TV tower in Kyiv, Ukraine said.
• Ukraine's Defense Ministry warned that television channels will temporarily stop working, but backup broadcasts may return shortly, according to a translation of a tweet from the agency's official account.
• The alleged strike comes as recent satellite imagery appears to show a miles-long convoy of Russian military forces headed toward Kyiv, spreading fears that the capital city could soon face a full-scale assault.

EDITOR'S NOTE: GRAPHIC CONTENT: Photos show casualties and destroyed infrastructure in Ukraine.

Russian forces have struck a TV tower in Kyiv, Ukraine said Tuesday.

Ukraine's Defense Ministry warned that television channels will temporarily stop working, but backup broadcasts may return shortly, according to a translation of a tweet from the agency's official account.

A senior U.S. Defense official appeared to reference the attack later Tuesday morning.

"We've seen open press images of at least one strike on a government building in Kyiv. But that's the only one that I'm aware of," the person, who spoke on condition of anonimity, told reporters.

The alleged strike comes as recent satellite imagery appear to show a miles-long convoy of Russian military forces headed toward Kyiv, spreading fears that Ukraine's capital city could soon face a full-scale assault. Russia has set its sights on Kyiv since it invaded its neighbor last week.

But the U.S. official also said there are indications that the Russian move on Kyiv has stalled, and that some Russian units have surrendered without a fight.

Fighting has already shaken other Ukrainian cities such as Kharkiv, which lies to the east of Kyiv near the Russian border. Residents seeking cover from Russian bombs and shelling have fled underground into the city's metro stations.

— CNBC's Amanda Macias contributed to this report.

This is developing news. Please check back for updates.