Masked gunmen attacked the offices of a French satirical magazine that has drawn repeated threats for its caricatures of the Prophet Muhammad, killing at least 12 people, including at least four journalists and two police officers.
Police said 10 people were wounded in the January 7 attack on the weekly Charlie Hebdo in Paris.
At the scene shortly after the late-morning attack, French President Francois Hollande called it "an act of terrorism" and said four of the wounded were in critical condition. Hollande was reportedly to hold an emergency government meeting later in the day.
France raised its alert status for Paris to the highest level -- "attack alert" -- and Hollande said that "several terrorist attacks were thwarted in recent weeks."
"We are threatened because we are a country of liberty," he said.
In a video recorded by a man taking refuge on a nearby rooftop, shouts of "Allahu Akbar" (God is greatest) can be heard between rounds of heavy arms fire.
Witnesses cited by police said the attackers shouted: "We have avenged the prophet."
Most of the victims worked at the magazine’s newsroom, said Matthieu Lamarre, a spokesman for the Paris mayor’s office.
French media reports cited a lawyer for Charlie Hebdo as saying that the dead included Editor in Chief Stephane Charbonnier, known as Charb, and cartoonists known as Cabu, Tignous, and Wolinski -- household names in France.
A cartoonist for Charlie Hebdo, Coco, said the attackers spoke perfect French and claimed they were linked to Al-Qaeda.
"I had gone to pick my daughter up from day care, when I arrived in front of the door of the magazine's building two armed men wearing balaclavas brutally threatened us," she said. "They wanted to get in, to go up. I dialled the code."
She said the attackers shot at staff for five minutes, and that she hid under a desk.
The lawyer also said that one of the police officers who were killed was guarding Charbonnier, who had received numerous death threats over the years.
Luc Poignant, an official of the SBP police union, said the attackers escaped in two vehicles.
A video attributed to France 24.com appeared to show attackers in black balaclavas shooting a person -- believed to be a police officer -- as he lay wounded on the street before getting into a small car and leaving the scene.
Witness Benoit Bringer told a local TV station, "About a half an hour ago, two black-hooded men entered the building with Kalashnikovs. A few minutes later, we heard lots of shots," he said, adding that the men were then seen fleeing the building.
PHOTO GALLERY: Images from the attack
U.S. President Barack Obama said in statement that he condemned the "horrific shooting" in Paris and said he had directed his administration to provide any assistance needed "to help bring these terrorists to justice."
German Chancellor Angela Merkel said in a statement that the shooting in Paris is not only an attack on French citizens, but on "freedoms of press and speech."
British Prime Minister David Cameron condemned the attack on Twitter.
"The murders in Paris are sickening. We stand with the French people in the fight against terror and defending the freedom of the press," he said in a tweet.
Kremlin spokesman Dmitry Peskov said that Russian President Vladimir Putin expressed condolences and that Russia "decisively condemns terrorism in all its forms."
Satirical weekly Charlie Hebdo drew international attention in February 2006 when it reprinted cartoons of the Prophet Muhammad that had originally appeared in Danish daily Jyllands-Posten, sparking a wave rage across the Muslim world.
Its former editorial offices were firebombed in November 2011 when it published a cover featuring a cartoon of Muhammad and under the title "Charia Hebdo."
Despite being taken to court under antiracism laws, the weekly continued to publish controversial cartoons of the Muslim prophet.
In September 2012, Charlie Hebdo published cartoons of a naked Muhammad as violent protests were taking place in several countries over a low-budget film, titled "Innocence of Muslims," which was made in the United States and insulted the prophet.
Its latest tweet, earlier on January 7, was a cartoon of the leader of the Islamic State militant group, Abu Bakr al-Baghdadi.
The January 7 attack came on the same day a new book imagining France in 2022 coming under Islamic rule hit French bookshops. Soumission, or Submission, is the latest novel by French author Michel Houellebecq.
Charlie Hebdo's cover this week refers to Submission.
The attack also comes after tens of thousands of people again took to the streets in several German cities in rival rallies for and against a new group which opposes what it claims is the Islamization of Europe.
In its latest show of strength, Patriotic Europeans Against the Islamization of the West (PEGIDA) drew some 18,000 people to a demonstration January 5 in Dresden and smaller crowds to rallies in other German cities.
With reporting by AP, Reuters, AFP, and CNN