LONDON -- Armed British police carried out an early-morning raid on a residential address near London's Olympic Park on Thursday, using smoke grenades and a stun gun in what they called a pre-planned anti-terror operation.
A total of six people were arrested there and in separate raids in other parts of the capital, but Scotland Yard said the operation was not linked to the upcoming games, due to kick off on July 27.
Police didn't identify the suspects, who range in age from 18 to 30.
However Mizanur Rahman, who is involved with a Muslim activist group, said all those arrested were British Muslims. He said the three men taken into custody in Stratford, the neighborhood that contains Olympic Park, were brothers and claimed that one was a former police officer.
A police press officer declined to comment on the claim.
Resident John Smallshaw said a raid took place at a residence on Abbey Road, only about a mile (1.6 kilometers) from the Olympic Park.
He told The Associated Press he was awoken just after 4 a.m. by "five loud bangs in quick succession" and saw police raiding the home. He said he later witnessed "one young man taken on foot to a waiting ambulance."
Another man was later taken into an unmarked police car, Smallshaw said, adding that plainclothes officers were still at the premises.
Continuing searches are being carried out at eight separate addresses in east, west and north London and at one business in east London, police said. Rahman identified one of the addresses as being in Old Street, near London's financial district.
Police said all the suspects have been taken to a southeast London police station.
Intelligence officials say there has been an expected increase in chatter among extremist groups ahead of the games, but there are still no specific or credible threats targeting the Olympics. The terror level is labeled substantial, a notch below severe. A substantial threat level indicates that an attack is a strong possibility.