Authorities in Britain say there will be no reduction in their massive anti-terrorist operation despite the capture of four men suspected of trying to bomb London's transit system.

In London and Rome, police are beginning their interrogation of the suspects Saturday. Officials say the arrests appear to have given investigators a rare prize, a full cell of alleged terrorists, captured alive and unharmed.

The head of London's anti-terrorist task force, Peter Clarke, says specialist tactics - apparently stun grenades and tear gas - were used to arrest two suspected bombers, Ibrahim Muktar Said and Ramzi Muhammad, when they refused to surrender to police Friday.

In a separate operation in Rome in Friday, Italian police arrested a third suspected bomber, Hussain Osman, said to be a British passport holder who was born in Ethiopia. Britain is asking for his extradition.

The fourth suspect, Yasin Hassan Omar, was apprehended on Wednesday in Birmingham.

Mr. Clarke says there is still a risk of terrorist attacks, and he urged all Britons to remain alert as officials continue investigating this month's attacks -- four explosions on July 7 that killed more than 50 people and a failed attempt to detonate at least four more bombs two weeks later, on July 21.