The British police are searching for an Asian said to be a suicide bomber for Al Qaeda.

He is one of two suicide bombers -- the other is a black Muslim convert -- trained in Afghanistan and now believed to be on the loose in Britain.

Security has been stepped up after a wave of suicide bombings on Western targets in Saudi Arabia and Morocco.

The threat to the UK is being taken so seriously that armed elite undercover squads have been given permission to implement a shoot-to-kill policy, if they believe an attack is imminent.

Last week Osama bin Laden's deputy, Ayman Zawahiri, sent out a chilling message that called on Muslims to attack the 'missions' of Britain and America and to follow the example of the September 11 hijackers.

Drawings of the two suspects have been circulated within the M15 intelligence service and Special Branch police. According to reports they were made by an American artist from descriptions given by detainees in the Guantanamo Bay camp in Cuba, where 680 terrorist suspects are being held, including seven from Britain.

The prisoners are said to have told authorities that the two men were members of a specially recruited squad.

Professor Paul Wilkinson, head of the Centre for the Study of Terrorism and Political Violence, warned suicide bombers could be part of a larger cell.

"I would be surprised if there were only two people. It is more than likely that these two are the top of the list of people they would like to interview," he said.

"It is very unlikely that this network would rely on two individuals to carry out operations in this country. They would have colleagues in an operational cell and if the plans were complicated in any way they would also have a support network."

Earlier this month a self-styled recruiter of British volunteers for an Islamic holy war, Hassan Butt, claimed more than 50 people in the UK were waiting for the chance to become suicide bombers.

His warning followed a suicide attack on a Tel Aviv bar by two British Pakistanis, Omar Sharif, from Derby, and Asif Hanif, from London, which raised the possibility of suicide squads based in Britain.

Richard Reid, the 'shoe bomber' who tried to blow up a passenger flight in December 2001, attended a mosque in London's Finsbury Park. So also did Frenchman Zacharias Moussaoui, the alleged 20th hijacker on September 11.

According to reports the black Muslim convert was at Feltham young offenders institute near London airport at the same time as Reid, who was jailed for life earlier this year.

Meanwhile, British MPs are demanding an urgent probe into how thousands of passports that go missing every year could fall into terrorists' hands.

Opposition Liberal Democrat MP Paul Burtsow has uncovered statistics that show 11,500 British passports were lost over the last four years after they were posted back by the UK Passport Agency and never arrived.

"Either there is incompetence on the part of Royal Mail sorting offices... or there is a black-market trade in stolen passports," Burtwo said.