Hooded gunmen who stormed the Paris offices of a satirical magazine known for lampooning Islam and other religions, killing at least 12 people yesterday, were still on the loose last night.

Police staged a huge manhunt for the attackers, who escaped after shooting dead some of France’s top cartoonists at the Charlie Hebdo weekly, as well as two police officers.

One of the assailants was captured on video outside the building shouting “Allahu Akbar!” (God is greatest) as shots rang out.

Another walked over to a police officer lying wounded on the street and shot him point-blank in the head with an assault rifle, before the two calmly climbed into a black car and drove off.

The scene in the offices was described as carnage

A police union official said the assailants, three in total, remained at liberty and there were fears of further attacks. The official described the scene in the offices as carnage, with a further four wounded fighting for their lives.

Tens of thousands joined impromptu rallies across France in memory of the victims and support for freedom of expression. The government declared the highest state of alert, tightening security at transport hubs, religious sites, media offices and department stores as the search for the assailants got under way.

Some Parisians expressed fears about the effect of the attack on community relations in France, which has Europe’s biggest Muslim population.

“This is bad for everyone – particularly for Muslims, despite the fact that Islam is a fine religion. It risks making a bad situation worse,” Cecile Electon, an arts worker who described herself as an atheist, told Reuters at a vigil on Paris’s Place de la Republique attended by 35,000 people.

Charlie Hebdo (Charlie Weekly) is well known for courting controversy with satirical attacks on political and religious leaders of all faiths and has published numerous cartoons ridiculing the Prophet Muhammad. Jihadists online repeatedly warned that the magazine would pay for its ridicule.

The last tweet on its account mocked Abu Bakr al-Baghdadi, the leader of the militant Islamic State, which has taken control of large swathes of Iraq and Syria and called for “lone wolf” attacks on French soil.

There was no claim of responsibility. However a witness quoted by 20 Minutes, a daily newspaper, said one of the assailants cried out before getting into his car: “Tell the media that it is al Qaeda in Yemen!”

Supporters of the Islamic State and other jihadist groups hailed the attack on internet sites. Governments throughout Europe have expressed fear that fighters returning from Iraq or Syria could launch attacks in their home countries and may now review their own security.

French President Francois Hollande speaks on yesterday’s killing. Photo: Reuters

“Today the French Republic as a whole was the target,” President Francois Hollande said in a prime-time evening TV address, declaring a national day of mourning on Thursday.

An amateur video broadcast by French television stations shows two hooded men all in black outside the building. One of them spots a wounded policeman lying on the ground, hurries over to him and shoots him dead at point-blank range with a rifle.

In another clip on Television station iTELE, the men are heard shouting in French: “We have killed Charlie Hebdo. We have avenged the Prophet Muhammad.”

Paris prosecutor Francois Molins said the assailants killed a man at the entrance of the building to force entry. They then headed to the second floor and opened fire on an editorial meeting attended by eight journalists, a policeman tasked with protecting the magazine’s editorial director and a guest.

“What we saw was a massacre. Many of the victims had been executed.”

What world leaders said

US President Barack Obama condemned the shooting, calling it a terrorist attack against its ally, France, and offering assistance.

“We are in touch with French officials and I have directed my administration to provide any assistance needed to help bring these terrorists to justice,” he said.

“France is America’s oldest ally, and has stood shoulder to shoulder with the United States in the fight against terrorists who threaten our shared security and the world,” Obama said.

“Time and again the French people have stood up for the universal values that generations of our people have defended.

“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,” he said.

British Prime Minister David Cameron said: “The murders in Paris are sickening. We stand with the French people in the fight against terror and defending the freedom of the press.”

UN Secretary General Ban Ki-moon said: “It was a horrendous, unjustifiable and cold-blooded crime. It was also a direct assault on a cornerstone of democracy, on the media and on freedom of expression.”