“We have four people in custody we believe are the images we released," said a police official, who asked not to be named in accordance with British practice. He was referring to closed circuit television pictures of four suspects released after the attacks.
Police carried out raids in west London on Friday, arresting three suspects, two of whom are suspected of being the bombers. Another suspect was arrested in Birmingham on Wednesday. In Rome, Italian police arrested another suspected bomber on Friday.
Earlier Friday, Police arrested three men in west London's Notting Hill neighborhood and said they were connected to the failed attacks.
"Two men were arrested at one address and one man was arrested at another address," Metropolitan Police spokesman said on customary condition of anonymity.
Police did not identify the suspects, Britain's Press Association news agency said one was believed to be Muktar Said Ibrahim, 27, who allegedly tried to blow himself up on a bus in Hackney, east London.
It said another was believed to have been responsible for an attempted bombing near Oval Tube station on the same day.
Two women detained
Ibrahim is also known as Muktar Mohammed Said. He came to Britain in 1990 from Eritrea, was granted residency in 1992 and British citizenship in September 2004. The Oval tube bomber, whose name was not released, was the man wearing a distinctive "New York" sweatshirt on closed circuit television images released by police.
It was unclear who the third man arrested in Notting Hill was.
Another man in custody has been identified as Yasin Hassan Omar, 24, a Somali citizen with British residency. Omar is suspected of trying to blow up the Warren Street subway station on July 21. He was arrested in Birmingham on Wednesday.
Separately, two women were arrested on the main concourse of London's Liverpool Street rail station on Friday. The Metropolitan Police said in a statement that they had been arrested under the anti-terrorism act, but it was unclear if they were directly linked to the July 21 attacks.