A British Muslim has apparently been filmed alongside Al Qaeda fighters in the Pakistan-Afghanistan border area for the first time.
A recently released militant martyrdom video shows a man dubbed 'Musa the British' in a montage of fighters who have died either as suicide bombers or in firefights against Coalition forces.
'Musa' is thought to be in the Waziristan area of Pakistan - and is also the first Briton to appear on an Al Qaeda suicide video since the 7/7 bombings.
That has raised fears over future terror attacks on UK soil, with security services concerned the man was accompanied by other Britons who could be planning an operation.
The internet video glorifying militants shows a bomb attack on a U.S. Army convoy and a suicide bomb attack in Iraq.
The montage of dead militants includes 'Musa', a bearded man shown praying and an on-screen message adds 'may God have mercy on his soul'.
Experts say it is a 'fair assumption' that the man may have been a suicide bomber.
Security services including MI5 are said to be alarmed at the emergence of the video showing a Briton thought to have been made in the Waziristan area of Pakistan.
'Musa the British' is shown alongside other dead suicide bombers and fighters, in a montage set to a music that is designed to recruit new terrorists.
MI5 officers are reportedly trying to identify the man and determine whether he was accompanied by other Britons in the Pakistan border with Afghanistan - a hub of al Qaeda planning activity.
The video begins with a clip of 'Yusuf al-Kuwaiti' driving to a suicide bomb attack in Iraq with on-screen subtitles that read: 'Right now I am feeling such a felicity in my heart that it can’t be understood by anyone except Allah.
I make duaa [supplication] to Allah to grant me steadfastness until I meet him drenched in blood.”
It is followed by footage of Taliban fighters and Western troops, inter cut with the bodies of militants being prepared for funeral.
The music is a traditional Islamic nasheed in Urdu, suggesting the vide was made in Pakistan, with lyrics translated as: 'In our lifetime we longed for this one desire, our chests be adorned only with bullets.
'Always searching for death in its very valleys, we readied ourselves to lay down our lives and kept searching.'
'Musa' is the first apparent Briton to appear in a terrorist martyr video since July 7 bombers Mohammed Sidique Khan and Shehzad Tanweer, whose suicide videos were released in 2005 and 2006.
Neil Doyle, an expert in extremist videos, said: 'It's the first militant propoganda video to show a British fighter on the ground. It's a fair assumption that he may have died as a suicide bomber. Lots of the other militants are displayed as martyrs.
'One of them is a car bomber shown driving to his attack. It suggests Musa died in similar circumstances.
'A few videos have come out in the new year, summarizing who has died and the fighting that has taken place.
'Musa is likely to have been in the North Waziristan area of Pkistan. That's where the Pakistan Taliban and the Afghan Taliban launch raids into Afghanistan.'
The video first appeared in August but was last week re-released with English subtitles.
It emerged as British Airways employee Rajib Karim was convicted of planning a 'spectacular' attack in co-ordination with Al Qaeda in Yemen.
The Home Office refused to comment on investigations by the Security Services.