In the latest alarming evidence of child soldiers being used by Syrian rebel forces, an Islamist brigade linked to Al Qaeda released footage of a four year old it claimed as its youngest recruit.

In the video (below), the child - who can barely hold the AK-47 rifle he is firing - lets off two shots to cheers of "Allahu Akbar". The tiny boy is clad in a black ski mask and is forced to rest the barrel of the rifle on what appears to be a section of a roadblock to prevent himself from falling over.

Britain's Daily Mail reported that the child is believed to be the son of an Albanian jihadi, one of thousands of foreign Islamist fighters who have flocked to fight on both sides of the Syrian civil war, which is increasingly being waged as a sectarian conflict between Islam's Shia and Sunni sects.

In December, a video by the Middle East Media Research Institute (MEMRI) illustrated the numerous cases of young Syrian children - often orphans who parents were killed by the Assad regime - fighting among the ranks of the country's various rebel factions.

The video comes as French Prime Minister Francois Hollande claimed that both France and the UK had seen up to 700 foreign Islamist fighters from each of their countries leave to fight in Syria.

"We have young people who live in our respective countries who are being manipulated, and they are going off to the combat areas," he said after a press conference with his British counterpart David Cameron. "Today we were exchanging figures – 600 to 700 young people are involved in each of our countries."

Western security officials are concerned that some of the scores of fighters from Europe and North America could eventually return - radicalized and well-trained - to their native countries and commit attacks there.

Earlier this month a report revealed how an Islamist network led by British Muslim extremist Anjem Choudary was actively recruiting young British Muslims to fight in Syria, under the noses of British authorities.