The Metropolitan Police will be allowed to detain 14 more suspects; three people until tomorrow, and the remaining 11 until Friday, the spokeswoman said. Under British anti-terror laws, police can detain terrorism suspects for up to 28 days without charging them with an offence, subject to regular court approval.

The 14 were arrested in police raids in London overnight Saturday on suspicion of planning acts of terrorism, prompting searches, including one at an Islamic school. The police spokeswoman also said that 17 searches were ongoing in south, east and north London in connection with the investigation.

London?s Metropolitan Police said the suspects were detained ?on suspicion of the commission, preparation or instigation of acts of terrorism,? following a ?pre-planned, intelligence-led operation? lasting months. But they said the arrests were not linked to the July 7, 2005 suicide attacks that killed 56, including the four British Islamist extremist bombers.

Nor were they connected to the massive August 10 counter-terrorism operation against an alleged plot to blow up US-bound aircraft that led to more than two dozen arrests and unprecedented security measures at airports worldwide. Those arrested, aged between 17 and 48, were being grilled at the high-security Paddington Green police station in central London.

According to Britain?s domestic Press Association (PA) news agency, the men were thought to be mainly young British Muslims of Pakistani origin.

An unnamed security source quoted by PA said there was no evidence of any imminent attack and it was not yet clear if the men were part of one group or a number. Police have not revealed what prompted them to act.