Detectives have begun questioning the men suspected of carrying out attempted bomb attacks in London.
Two men were arrested in armed raids in London, and a third was captured in the Italian capital of Rome on Friday.
A fourth man was arrested in Birmingham on Wednesday. Police now believe they have caught the main suspects from the failed July 21 bomb attacks.
Police are trying to work out if a fifth man arrested was linked to a bomb found in west London last Saturday.
Suspected bombers arrested
1 - Yasin Hassan Omar, 24, suspected of trying to bomb a Tube near Warren Street. Arrested in Birmingham on Wednesday
2 - Muktar Said Ibrahim, 27, from Eritrea, suspected of leaving an explosive at the back of a bus in Hackney
3 - Third man, so far unnamed, wanted over attempt to bomb a Tube train between Stockwell and Oval tube stations
4- Osman Hussain, believed to be a naturalised British citizen born in Somalia, arrested by police in Rome
Friday saw lots of police action in London, as they carried out armed raids in Notting Hill and Kensington, arresting three people.
Two of the men arrested were named as Muktar Said Ibrahim, 27, the number 26 bus bomb suspect and Ramzi Mohammed who is wanted over the failed attempt to bomb a Tube train near Oval station.
They are now being held at a top security police station in London.
The suspect arrested in Rome is a UK citizen called Osman Hussain, also known as Isaac Hamdi. He is being questioned about the bomb attempt at Shepherd's Bush station.
Hussain had been staying there with his brother, who was also arrested, Italian officials said.
The UK government is hoping to have him sent to Britain for more questioning, after Italian officials have finished talking to him.
Detectives are still investigating the buildings in west London where they arrested two of the men suspected of carrying out the attacks.
Police said Friday's events were significant and added that the day was the most successful in the investigation so far.
But they also warned people to continue to be watchful and alert.