The men - believed to have links with Osama bin Laden, the alleged terrorist said to have ordered last month's US embassy bombings in East Africa - were picked up in a series of early-morning raids after a lengthy surveillance operation by MI5 and Scotland Yard's Anti-Terrorist Branch.
Mr bin Laden - a wealthy Saudi Arabian dissident, currently believed to be in Afghanistan - is wanted by America in connection with the 7 August attacks on its embassies in the Kenyan capital, Nairobi, and Dar es Salaam, Tanzania, in which more than 250 people were killed.
Security services fear Muslim fundamentalists have been planning to hit a number of American targets in retaliation for the United States cruise missile attack on a pharmaceuticals factory in Sudan, which was itself a reprisal for the embassy bombings.
Security has already been tightened at the US Embassy in Grosvenor Square, London, and other high-profile locations such as the Planet Hollywood restaurant in Leicester Square. The Cape Town branch of the American-owned restaurant chain was bombed last month.
All the men arrested yesterday at seven addresses in north-west and west London were being interviewed last night by police. An eighth address, believed to be business premises, was being searched.
Armed officers were not deployed during the arrests, known as Operation Challenge, and Scotland Yard stressed last night that there had been no threat of an imminent terrorist attack. Scotland Yard has kept the FBI informed about the operation. The arrests, under Section 14 of the Prevention of Terrorism Act 1989, are not believed to have been linked to any unsolved terrorist incident. Nor were the raids connected with recent changes in anti-terrorism laws giving police the right to act against suspected terrorists plotting attacks in other countries.
Bakri Muhammad, a spokesman for the International Islamic Front, which supports Mr bin Laden's wider aims, said the seven men arrested were all political refugees who had fled Egypt after campaigning against the government there.
Mr Muhammad said they were "well-known political refugees". He added: "They publish leaflets and send faxes - they have nothing to do with terrorism or Bin Laden."
He said the men had been in Britain for more than four years and belonged to a number of Egyptian Islamic movements. "These men are well known by the Special Branch."
Mr Muhammad said that when the men were arrested they had all gone with the police peacefully. Their families are now staying with friends living near by.
The FBI believes that Mr bin Laden's organisation, Al Qaeda, is committed to murdering American military personnel stationed in Saudi Arabia, Yemen, Somalia and elsewhere. The group has also issued threats against ordinary American citizens, saying they were a legitimate target.
Two men, one a Yemeni, Mohamed al-Owhali, and the other a Kenyan citizen, Mohammed Howaida, have already been flown to the US to stand trial for the Nairobi embassy bombing.
The FBI is seeking a third man, Haroun Fazil, from the Comoros Islands, in connection with the embassy bombings, and it has offered a reward of up to $2m (pounds 1.3m) for information leading to a conviction.
Yesterday's arrests in London were made by officers from Scotland Yard's Anti-Terrorist Branch, commanded by Deputy Assistant Commissioner Alan Fry. They were acting, in part, on information supplied by MI5, which is known to have been stung by criticism that London is a hot-bed of international terrorism.
Senior Yard sources admit that London, like other capital cities, is a "target-rich" environment for fundamentalist groups who are intent on pursuing a holy war against America or Britain.
But they say police are more concerned about the risk of a maverick group committing a "one-off" random attack on a high-profile commercial target, which is impossible to predict or plan for.
The last serious Middle-East-inspired attack in London was in 1994 when two Palestinians planted a car bomb outside the Israeli Embassy, causing pounds 5m damage and injuring 13 people, and a further device outside the offices of a Jewish charity in Finchley.
Last month, the Government gave itself new powers under the Criminal Justice (Terrorism and Conspiracy) Act to allow the prosecution of people found to be plotting terrorist acts abroad. Police emphasised that yesterday's arrests were not connected to the new legislation.Reuse content