Some 4,000 Britons have received training at al-Qaida camps in the past 10 years and most of them are back in Britain, the Independent reported on Friday.
The newspaper quoted security sources as saying that many of those returning from Afghanistan have been traced, but others have disappeared. The sources also said that most of the former volunteers are not seen as threats but some are believed to have retained their terrorist loyalties.
The training took place mainly at camps in Afghanistan, and an al-Qaida network stretching across Europe had arranged the Islamic volunteers to travel to the terrorist camps and then return home.
The number of British Muslims volunteered to fight for Osama bin Laden's organization and the Taliban regime in Afghanistan is far greater than was previously known, the paper said.
Many of the British Muslims fought in the Taliban ranks against the Northern Alliance and other recruits are believed also to haveseen action in Bosnia and Chechnya, added the paper.
The paper also quoted Western intelligence officials as saying that Britain's close alliance with the United States in the "war on terror" and the deployment of troops in Afghanistan means that it is a prime target for terrorist attacks.