NYPD Commissioner Bill Bratton said the force is redistributing manpower around New York City after two police officers and 10 journalists were killed in a shooting Wednesday at the Paris, France, offices of a satirical magazine.
NYPD officials said counterterrorism patrols were placed at landmarks throughout New York City, including at the French Consulate and several media company offices, Wednesday morning after the attacks at the Charlie Hebdo office -- the country's deadliest terrorist attack in recent memory.
At a news conference Wednesday, Bratton said the attack in France was "very concerning" but added that no direct threats had been made against any groups or organizations in New York City.
MTA security officials also said they monitoring the events in France. The transit authority stepped up security at subway and train stations in September after the Iraqi Prime Minister claimed during a United Nations briefing that his country's intelligence agency had uncovered a plot against the city. National Guardsman and police were both seen at Grand Central Terminal Wednesday.
The NYPD's enhanced security measures come hours after masked gunmen shouting "Allahu akbar" stormed into the Parisian office and opened fire. They killed 12, including the magazine's editor, and injured eight before fleeing in a getaway car.
Hollande called the slayings "a terrorist attack without a doubt" and said several other attacks have been thwarted in France "in recent weeks."
Over 100 people gathered in Union Square Wednesday night to show their support for the victims of the attack. They chanted "We are not afraid" and held signs in English and French saying "We are Charlie." They also lit candles at a makeshift memorial.
French authorities have identified the suspects as Said Kouachi and Cherif Kouachi, both French and in their early 30s, and 18-year-old Hamyd Mourad, whose nationality wasn't immediately clear.
U.S. counterterrorism officials told NBC News late Wednesday they cannot be certain what the status is of the three suspects, citing conflicting information from French sources.
Clad all in black with hoods and machine guns and speaking flawless French, the attackers forced one of the cartoonists at the weekly Charlie Hebdo -- at the office with her young daughter -- to open the door.
The staff was in an editorial meeting and the gunmen headed straight for the paper's editor, Stephane Charbonnier -- widely known by his pen name Charb -- killing him and his police bodyguard, said Christophe Crepin, a police union spokesman on the scene. Minutes later, two men strolled out to a black car waiting below, calmly firing on a police officer, with one gunman shooting him in the head as he writhed on the ground.
"Hey! We avenged the Prophet Muhammed! We killed Charlie Hebdo," one of the men shouted, according to a video filmed from a nearby building and broadcast on French television. Other video images showed two gunmen in black at a crossroads who appeared to fire down one of the streets. A cry of "Allahu akbar!" -- Arabic for "God is great" -- could be heard among the gunshots.
The gunmen abandoned their car at the northern Porte de Patin and escaped, Paris police said.
Corinne Rey, the cartoonist who said she was forced to let the gunmen in, said the men spoke fluent French and claimed to be from al-Qaida. In an interview with the newspaper l'Humanite, she said the entire shooting lasted perhaps five minutes.
France raised its security alert to the highest level and reinforced protective measures at houses of worship, stores, media offices and transportation. Top government officials held an emergency meeting and Hollande planned a nationally televised address in the evening. Schools across the French capital closed their doors.
Both al-Qaida and the Islamic State group have repeatedly threatened to attack France. Just minutes before the attack, Charlie Hebdo had tweeted a satirical cartoon of the Islamic State's leader giving New Year's wishes. Another cartoon, released in this week's issue and entitled "Still No Attacks in France," had a caricature of a jihadi fighter saying "Just wait -- we have until the end of January to present our New Year's wishes."
Charlie Hebdo has been repeatedly threatened for its caricatures of the Prophet Muhammad and other controversial sketches. Its offices were firebombed in 2011 after a spoof issue featuring a caricature of the prophet on its cover. Nearly a year later, the publication again published crude Muhammad caricatures, drawing denunciations from around the Muslim world, since Islam prohibits the publication of drawings of its founder.