Image caption Call to jihad: British man shows off his gun

The BBC has seen an online video of a British man recruiting people over the internet to fight jihad in Syria.

The man, who is not identified but speaks with a London accent, is seen loading and firing a gun into the air.

The video invites Muslims to leave the "gangster life behind and join the life of jihad".

It has not been possible to verify its authenticity but an online extremism expert says it is a sign of al-Qaeda's growing "brand" in Syria.

Beheadings

Wearing a black balaclava, the subject of the video addresses the camera, saying: "I'm in the land of jihad at the moment with a Glock 19. Most of you playboys ain't seen that yet. I've got a box of ammunition from our so-called brothers, the Free Syrian Army. "

The man then loads the semi-automatic pistol and asks: "Where are you when we need to start taking heads off? Where are you when they are slaughtering our children and our fathers?" Soon afterwards he fires the guns into the sky before declaring "God is great" in Arabic.

The video, which was filmed at night, was posted on a website describing itself as an official online source of mujahideen material. The site used to post the video is believed to be linked to the Islamic State of Iraq and the Levant (ISIS), one of the main jihadist groups fighting government forces in Syria. Its ranks include many foreign jihadists.

The website appears to have been written by a native English speaker and the man in the video is captioned as an "ISIS mujahid".

Laith Alkhouri, a senior analyst of extremist content online with US-based analysts Flashpoint Global Partners, said it was posted on 17 December on a site which carries gruesome images of the killing of Syrian soldiers, including beheadings.

It also contains images that it claims are of dead Shia fighters, referring to them as "tourism photos".

"This is yet another troubling sign of the intensification of the 'al-Qaeda' brand of jihad in Syria," said Mr Alkhouri. "This is another sign on the rise of foreign fighters flocking into Syria for jihad, especially from the West. As jihadists gain momentum in certain strategic areas in Syria's north, the flocking of foreign fighters complicates Western efforts in countering [the] jihadist expansion on the Turkish borders.

"Considering that many of them are essentially unknown to their governments, their return home may go unnoticed by the security apparatus."

The British Security Service, MI5, has warned that the number of people who have travelled from the UK to fight in Syria is in the "low hundreds". Director General Andrew Parker told MPs that the conflict was attracting al-Qaeda sympathisers from the UK.

Earlier this week the BBC reported how a British man was killed fighting with ISIS. Ifthekar Jaman, from Southsea, Hampshire, told Newsnight in an interview from Syria in November that it was his "duty to fight" because Muslims were "being slaughtered". Mr Jaman's family told the BBC that he was killed while fighting forces loyal to the government.