A new group of British Muslims, particularly of Pakistani origin, was believed to be intent on staging another strings of blasts yesterday. The terrorists are said to have links to the Leeds attackers who caused the 7/7 blasts.

US security sources informed the British government yesterday that this third group of would-be attackers met at Finsbury Park mosque in North London, where some of the 7/7 terrorists are also known to have stayed, The Times reported.

Meanwhile, police are planning to pick out young Muslims for stop-and-searches as part of the security response to the bombings.

Hazel Blair, the Home Office Minister, defended the plan to the BBC yesterday, saying she believed the Muslim community would accept such searches as a necessary response.

The transport police also made it clear that it will target 'specific ethnic groups' in its hunt for terrorists.

Ian Johnston, the chief constable of the British Transport Police, said: "We should not waste time searching old white ladies."

He said he was confident there was every sign that the Muslim community understood the predicament that officers faced and that it would continue to support the police even if young Asians become the focus of most searches.

But Shami Chakrabarti, the director of the civil rights group Liberty, said that "racial profiling" was a disaster and could play into the hands of those who wanted to recruit terrorists.

Meanwhile, police said yesterday's arrests of five suspected bombers in house raids in Birmingham, London and Rome has not ended the threat. Deputy Assistant Commissioner Peter Clarke, head of the anti-terrorist branch, said: "The threat remains and is very real."

Authorities are now worried about how long such a huge contingent of policemen 6,000 strong can be mobilized for such intensive operations to "lock down London" while a threat remains. Police leave has been cancelled, costing Britain an additional 500,000 pounds to ensure security. Police are still on the hunt for the key persons behind organising and planning the terror cells.

The disclosure that Hussain Osman, a suspected bomber in the botched July 21 attempt, had fled to Paris unchallenged by using the Eurostar train at Waterloo has compelled Britain to think of reintroducing permanent passport checks at all British border points.

The government contends that Osman's slip from the country exposed that Britain's border is porous.

Outgoing British passport checks were abandoned at the Eurostar terminus last year. The Home Office said that checks by British immigration officials at embarkation points were reintroduced at the request of the police after the 7/7 bombings but lifted on July 17. They were introduced again after the July 21 attacks and were still in force.

Osman, also known as Hamdi Issac, apparently got through despite CCTV pictures of the bombing suspects being displayed prominently at Waterloo.