Shortly afterward, Hollande declared a state of emergency across France and closed its borders.

“This is a horrible ordeal that, once again, assails us,” he said. “Faced with terrorism, France needs to be strong.” French media noted that it was unusual for a French president to make such statements while many things are yet unclear.

U.S. President Barack Obama gave a brief statement to reporters Friday evening at the White House. "Once again, we've seen an outrageous attempt to terrorize innocent civilians," he said.

"We stand prepared and ready to provide whatever assistance that the government and the people of France need," he said, and he pledged to "bring these terrorists to justice and go after any terrorist networks" involved.

U.S. Secretary of Homeland Security Jeh Johnson also issued a statement saying that the Department of Homeland Security and Federal Bureau of Investigation are not aware of "specific or credible threats of an attack on the U.S. homeland of the type that occurred in Paris tonight" but that they were working with local law enforcement officials to ensure the public’s safety.

U.S. Capitol police said they were monitoring events in Paris and had enhanced patrols throughout Capitol Hill "out of an abundance of caution."

American Airlines on Friday evening suspended all flights to Paris' Charles de Gaulle Airport and is "awaiting additional information," an airline spokesman told Le Figaro.

After the attacks, witnesses described scenes of fear and confusion in neighborhoods that are popular with young people and tourists and are packed on a Friday night.

"I was in the restaurant when the gunshots were heard. We fell to the floor with all the other diners. I didn’t see any gunmen. I was just looking at the floor," said Charlie Brehaut. "I saw a woman who was lying next to me, and I realized she had been fatally wounded in the chest, and there were a few more casualties."

Madeline Barry, who was at a different restaurant, told Al Jazeera that shortly after the attack, patrons filed out of the dining area into a courtyard.

"People are calling their families, trying to understand what is going on," she said. "There is a heavy police presence on the street."

Nick Holden, dining at a restaurant in central Paris, told Al Jazeera what he saw in the first moments after the shootings.

"A lady came in crying. We assumed some sort of domestic dispute, and someone said she had seen someone shot," he said. "We couldn't believe what was said until we heard the sirens and people started to run, and that’s what we did."

Parisians have been on edge since January, when two gunmen affiliated with Al-Qaeda in the Arabian Peninsula (AQAP) attacked the offices of Charlie Hebdo, killing 12 people, including much of the weekly's editorial staff and three police officers.

The assault on Charlie Hebdo was the beginning of three days of violence in the French capital, as a third gunman, in apparent coordination with the other attackers, shot and killed a policewoman and took several hostages at a kosher grocery store. All three gunmen were eventually killed by French security forces; four hostages were also killed in a police raid on the grocery store.

With wire services