Allied troops fighting in Afghanistan have long suspected that their Taliban opponents include Britishborn Muslims.
Thick Midlands and Mancunian accents have been picked up from enemy radio signals in the war zone.
But now there is fresh evidence that some of the Taliban were raised in the UK with the revelation that one fighter killed in a battle had an Aston Villa football club tattoo on his body.
A military source said: 'It was a shock to hear that the guys we were fighting against supported the same football clubs as us, and maybe even grew up on the same streets as us.'
The source said the body of the unidentified Muslim insurgent was found with the AVFC tattoo following clashes with the Nato-led International Security Assistance Forces.
The discovery adds to fears the Taliban is successfully recruiting hundreds of radicalised British nationals to fight against the country of their birth.
Tory MP Patrick Mercer, a former infantry commander, said the presence of a tattoo of an English football club suggests the insurgent had at one point been a well-integrated member of UK society who identified with his home culture, but was radicalised nevertheless.
Allied spy planes have previously picked up Birmingham and Manchester accents among Taliban radio chatter, while in April it emerged that a Briton had been identified as a Taliban bombmaker after his fingerprints were found on an unexploded roadside device in Helmand.
Details of forensic investigations on the bodies of dead Taliban fighters are normally top secret. But the military source said of the tattoo case: 'It's been well known for some time among soldiers in Afghanistan that at least one Aston Villa fan was fighting for the Taliban. A body of one of the men was found to have an AVFC tattoo on it.'
It is unclear when or where the body was discovered. Mr Mercer, MP for Newark and chairman of the Commons counterterrorism sub-committee, said: 'Radicalisation has been going on for some time now.
'We should not be surprised that individuals have essentially embraced the British culture but have then been suborned into enemies of the state.
'It just shows how insidious radicalisation is. We should be worried and disappointed and alarmed by this, but not surprised.'
A Government official, who asked to remain anonymous, said: 'There will always be a number of people who are radicalised in this country and want to leave the UK.
'The details of Aston Villa fans in the Taliban does not shock or surprise me. 'We have never had any hard and fast evidence to tie all of these snippets of information together, but we are sure they equate to a wider ongoing radicalism in the UK.'
The Foreign Office said: 'Wherever there is any firm evidence of Britons going abroad to wage jihad, we work with governments overseas to stop them.'
The Ministry of Defence said it was trying to corroborate the report of the tattooed insurgent.
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