Five men and one woman suspected of preparing terrorist attacks were on Thursday arrested during early morning police raids across London, the capital's Metropolitan Police said.
Police said the operation was not linked to the Olympics, which start in London on July 27, but was part of a planned intelligence-led operation.
In a separate and apparently unrelated incident, armed police closed both carriageways of a motorway near Britain's second biggest city, Birmingham, after reports of a man acting suspiciously on a coach heading for London.
A security source said the London arrests were related to international Islamist terrorism and were made at an early stage of plotting. It was not clear if any targets were identified.
During the raids, a 29 year old man was arrested on a street in west London while the others, aged between 18 and 30, were detained at residential addresses in east and west London.
A 24 year old man was tasered during the operation by armed police but did not require hospital treatment.
Police said the six were arrested on suspicion of the ``commission, preparation or instigation of acts of terrorism’’ and were taken to a police station in southeast London.
Detectives were searching eight homes in east, west and north London, and one business address in east London.
British security forces are on high alert for any signs of trouble ahead of the Olympics.
Seven years ago suicide bombers killed 52 people in a string of coordinated attacks in London.
In the Birmingham incident, coach operator Mega bus confirmed police were investigating an allegation against a passenger on the coach which had been travelling from Preston in north England to London.
All the passengers were taken off the coach and lined up on the tarmac of the M6 toll motorway just north of Birmingham.
Live helicopter television footage showed about 30 people sitting or standing inside a large rectangular police cordon.
Emergency vehicles and a bomb disposal unit were at the scene, the BBC reported. (Reuters/NAN)