At least 12 people were killed  when masked gunmen fired randomly at the office of a French satirical magazine that once courted controversy over its portrayal of the Prophet Mohammed.

Sky News quoted witnesses as saying that a number of men were involved in the deadly attack on the office of Charlie Hebdo. Ambulances rushed to the shooting site.

A journalist told iTele network that he saw several masked men armed with machine guns.

A dramatic photograph has been published in Le Monde newspaper of two gunmen dressed in black, standing either side of vehicle, apparently pointing their weapons at a police car.

And graphic footage taken from the top of a building shows a firefight in the street below, shouting and gunfire can be heard and two people can be seen levelling weapons.

There is also film of a police officer being executed by the gunmen as he lies on the ground, holding his hands up.

The dead are believed to include two police officers. Four people have also been critically injured.

Ambulances are at the scene.