The footage shows the two masked figures calmly returning to their getaway vehicle after murdering staff at the satirical magazine.

The pair reload their weapons, before one shouts: « We have avenged the Prophet Mohammed, we have killed Charlie Hebdo. »

It then shows the gunmen firing on a police car as they made their escape.

The vehicle, lights flashing, is forced to reverse at speed as the killers get out of their own car, aim their weapons and open fire.

The fundamentalist brothers Said and Cherif Kouachi killed 12 people in last Wednesday’s deadly attack on Charlie Hebdo, including two policemen.

Their accomplice, Amedy Coulibaly, gunned down a police officer before killing four people in a Jewish supermarket in the French capital.

In the wake of the atrocities, France’s Prime Minister has announced he would seek tighter surveillance of convicted extremists, amid reports the weapons used to kill 17 people came from outside the country.

Manuel Valls said « serious and very high risks remain » and warned the French not to let down their guard.

Christophe Crepin, a French police union representative, said several people were being sought in connection with the « substantial » financing of the attacks.

The funding and logistics involved indicated an organised network, he said.

http://news.sky.com/story