A new amateur video of the Charlie Hebdo gunmen has emerged, showing the two men calmly loading their weapons after the attack and shooting at a French patrol car which reversed in a narrow street to avoid the gunfire.

The video shows the two masked men calmly returning to their car after the attack on the satirical magazine on Jan 7, with one of them shouting: "We have avenged the Prophet Muhammad, we have killed Charlie Hebdo.''

In the video, the two men are seen placing their automatic weapons on the roof of the car and calmly loading their weapons while standing outside the car. They then get into the vehicle and drive along a narrow street where a police patrol car appears at the opposite end.

Undeterred, the gunmen get out of the car and open fire at the patrol car, which then reverses in the narrow street to avoid the gunfire. Second laters, the gunmen drive away while shooting out of the window.

According to the Telegraph, the man filming the dramatic gun battle is heard saying: "These are false bullets."

'No, they're not false bullets... Look at the cops. Look, look, they're reversing. They've smashed the cars.'

The gunmen - Cherif and Said Kouachi - attacked Charlie Hebdo's Paris office and massacred 12 people, saying they were taking revenge for previous publications of Prophet Muhammad cartoons - considered deeply offensive to many Muslims. The brothers had claimed to be linked to the terrorist group Al-Qaeda in Yemen.

A day later, a third gunman Amedy Coulibaly shot dead a policewoman in a southern Paris suburb.

Police launched a massive hunt for the three attackers which culminated in two hostage crises that gripped France and the rest of the world. Coulibaly stormed into a kosher supermarket in eastern Paris and seized shoppers, while the Kouachi brothers took one person hostage in a printing firm northeast of Paris.

After a tense stand-off, the brothers charged out of the building and were shot dead on Friday.

Moments later, security forces stormed the supermarket and killed Coulibaly. French authorities said four people were killed in the supermarket siege before police stormed the premises.