One of the men was captured on video shouting "Allah!" as four shots rang out. Two assailants were then seen calmly leaving the scene.

A police union official said the assailants remained at liberty and there were fears of further attacks.

Charlie Hebdo (Charlie Weekly) is well known for courting controversy with satirical attacks on political and religious leaders and has published numerous cartoons ridiculing the Prophet Mohammad.

Ten members of the Charlie Hebdo staff died in the attack, prosecutors said. Another 20 people were injured in the attack, including four or five critically.

A firebomb attack gutted the headquarters of Charlie Hebdo in November 2011 after it put an image of the Prophet Mohammad on its cover in what it described as a Shariah edition.

The last major attack in Paris was in the mid-1990s when the Algerian Armed Islamic Group (GIA) carried out a spate of attacks, including the bombing of a commuter train in 1995 which killed eight people and injured 150.