French officials say police have identified the three suspected gunmen in Wednesday's mass murder at the Paris headquarters of the satirical weekly paper "Charlie Hebdo."
Authorities say two of the alleged shooters are brothers who are French citizens, ages 34 and 32. The third suspect is an 18-year-old student. His nationality is not yet clear.
Police said at least 12 people, including two police officers, are dead after the attack.
Late Wednesday morning, black-hooded gunmen, who carried Kalashnikov rifles and a pump-action shotgun, stormed the weekly's offices, bursting into an editorial staff meeting and opening fire. Terrorism experts said the gunmen appeared to have carried out their attack methodically.
Ten members of the "Charlie Hebdo" staff died in the attack, prosecutors said. Among the dead were three cartoonists, including co-founder Jean “Cabu” Cabut and editor-in-chief Stephane “Charb” Charbonnier.
The gunmen said "Allahu akbar" and that they were avenging the Prophet Muhammed, Paris Prosecutor Francois Molins told reporters.
After dozens of shots rang out, two assailants were seen calmly leaving the scene in a video. One police officer was seen being shot as he lay wounded.
Official: Three assailants
A police union official said the assailants - in conflicting reports, Interior Minister Bernard Cazeneuve said there were three - remained at large and there were fears of further attacks.
The government declared the highest state of alert, increasing security at transport hubs, religious sites, media offices and department stores as the search for the assailants got under way.
At least 11 others were injured in the attack, including at least four critically. Police union official Rocco Contento described the scene inside the offices as “carnage.”
There was no immediate claim of responsibility for the attack.
"Charlie Hebdo" is well-known for courting controversy with satirical attacks on political and religious leaders and has published numerous cartoons ridiculing the Prophet Muhammad. Jihadists online have repeatedly warned that the magazine would pay for its ridicule.
Hollande defends press freedom
Charlie Hebdo, Paris
President Francois Hollande, who addressed the nation on television late Wednesday, rushed to the scene of what appeared to be a carefully planned attack. Sirens could be heard across the city.
“An act of indescribable barbarity has just been committed today in Paris,” Hollande said. He then defended the media: "No act of barbarity will ever extinguish freedom of the press."
In his nighttime address, Hollande denounced the shootings as a terrorist attack and said several other terror plots had been foiled in recent weeks.
"We were being threatened because we are a country of freedom. And because we are a country of freedom, we will fight against these threats and we will punish the aggressors."
He said, “Today, [the slain journalists] are our heros. And that is why tomorrow will be a day of national mourning, a decreed day. At 12 o'clock there will be a moment of contemplation in all public services."
France last year reinforced its anti-terrorism laws and is already on alert after calls from Islamist militants to attack its citizens and interests in reprisal for French military strikes on Islamist strongholds in the Middle East and Africa.
Hassen Chalghoumi, imam of the Drancy mosque in Paris's Seine-Saint-Denis northern suburb, said, "I am extremely angry. These are criminals, barbarians. They have sold their soul to hell. This is not freedom. This is not Islam and I hope the French will come out united at the end of this."
Chalghoumi, who also went to the site of the attack, said of the gunmen: “We must be firm with them, because they want terror, they want racism, they want to pit people against each other.”
US, world reaction
The White House strongly condemned the attack.
"France, and the great city of Paris where this outrageous attack took place, offer the world a timeless example that will endure well beyond the hateful vision of these killers," President Barack Obama said Wednesday, adding that America's thoughts and prayers are with the victims of the terrorist attack.
The White House said Obama has directed the administration to provide any assistance needed "to help bring these terrorists to justice."
In a joint appearance with Polish Foreign Minister Grzegorz Schetyna, Secretary of State John Kerry condemned Wednesday's Paris attack, saying, "Each and every American stands with you today."
Kerry said the U.S. stands with France in "solidarity and commitment" in "confronting extremism."
He also addressed the people of France in French.
Schetyna said his country is "deeply touched" by the attack, saying, "We stand together with France today."
German Chancellor Angela Merkel also condemned the shooting.
“This abominable act is not only an attack on the lives of French citizens and their security. It is also an attack on freedom of speech and the press, core elements of our free democratic culture," Merkel said.
U.N. Secretary General Ban Ki-Moon said such violence should be a unifying force.
"This horrific attack is meant to divide; we must not fall in to that trap. This is a moment for solidarity around the world, we must stand strong for freedom of expression and tolerance and stand against forces of division and hate."
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The New York-based Committee to Protect Journalists described the attack as a brazen assault on free expression.
The scale of the violence is appalling,” said CPJ Deputy Director Robert Mahoney. “Journalists must now stand together to send the message that such murderous attempts to silence us will not stand.”
The United Nations Security Council condemned the "barbaric and cowardly terrorist attack" at the Paris weekly's offices and called for the perpetrators to be brought to justice.
"The members of the Security Council strongly condemned this intolerable terrorist act targeting journalists and a newspaper," the 15-member council said in a statement.
U.N. High Commissioner for Human Rights Zeid Ra'ad Al Hussein joined a global chorus of condemnation against the "hideous crime," in Paris Wednesday. But while calling for the arrest and punishment of those responsible, Zeid cautioned against reacting with "discrimination and prejudice" against a wider group.
Upon entering the building, two gunmen headed straight for the paper's editor, Charbonnier, killing him and his police bodyguard first, Christophe Crepin, a police union spokesman, told The Associated Press.
A journalist from a press agency located just across the street described the scene to French radio, saying many shots were fired from Kalashnikov rifles. He then saw two armed and masked people leaving the building.
After fleeing into the street, the gunmen exchanged fire with officers in the first police car to respond to emergency calls and with two policemen on mountain bikes before firing repeatedly at a second patrol car.
The eyewitness said he heard yelling and shots being fired on the street, and that police and emergency services arrived a few minutes later.
The barbarity of the attack has left France in shock.
Amateur video filmed from a nearby rooftop showed a gunman walking up to a wounded policeman, who had staggered from the car to a nearby sidewalk, and shooting him dead point-blank.
The gunmen drove off toward northeastern Paris. They collided with a motorist before abandoning their car on a busy square and hijacking another vehicle as they escaped into the northern suburbs.
Wednesday's attack is considered one of the worst terrorist attacks on French soil in decades.
Late last year, a man shouting “Allahu Akbar” injured 13 people by ramming a vehicle into a crowd in the eastern city of Dijon. In 2012, seven people were killed in attacks that targeted French soldiers and Jewish civilians. In 1995, a series of attacks were carried out, including a commuter train bombing that killed eight and injured 150.
Charlie Hebdo supporters
Thousands of people took to Facebook and Twitter in support of the publication and the cartoon, saying freedom of expression must be defended.
Charlie Hebdo's offices were firebombed in 2011 after it published an issue poking fun at the Muslim prophet.
Muslims also denounced the weekly for later publishing a series of crude comics of the prophet.
Wednesday's shooting coincides with the launch of a controversial French book depicting France's election of its first Muslim president. Charlie Hebdo has featured the cover of the book, "Submission," on its cover.
Meanwhile, Danish media group JP/Politikens Hus, whose newspaper Jyllands-Posten published cartoons in 2005 depicting the Prophet Muhammad, has increased its security level because of the Parish shooting, an internal email showed.
Jyllands-Posten's publishing of the cartoons sparked a wave of protests across the Muslim world in which at least 50 died.
Victoria Macchi contributed to this report from Washington. Some material for this report came from Reuters and AFP.