The latest arrests were in Brighton. Police in Rome, aided by British investigators, have detained a brother of Osman Hussain, the fourth suspect. And ministers are considering tougher passport checks on travellers leaving the country amid embarrassment that Hussain, suspected of being the Shepherd's Bush station bomber, slipped undetected out of Britain on a Eurostar train as his picture was displayed around Waterloo station.
Police said the high-profile arrests did not mean the inquiry was being wound down or that the threat had diminished. Deputy Assistant Commissioner Peter Clarke, the head of the Anti-Terrorist Branch, said the threat remained very real and urged people to remain vigilant.
Detectives are still looking for others involved in the organising of both the 7 and 21 July attacks and are aware that more terror cells could exist.
A spokeswoman said: "We are searching for other people. We are not talking about cells. We have never spoken about a third cell. There were other people involved in the incidents of the 7th and the 21st. It's extremely likely there will be other people involved in harbouring, financing and making the devices."
Scotland Yard said the latest raids were on two addresses in Brighton where six men and a woman were arrested. The Yard said armed officers were not involved and those arrested were being interviewed at police stations in the Sussex area. A total of 20 people are now in custody and properties are still being searched.
Police said they would not be providing a "running commentary" on the questioning of Muktar Said Ibrahim, 27, accused of the failed Hackney bus bombing, Ramzi Mohammed, suspected of attempting the Oval Tube bombing, and his brother, Wahbi Mohammed, suspected of being a "fifth" bomber, all captured in raids in west London on Friday.
They are being held at Paddington Green police station in west London with Yasin Hassan Omar, 24, suspected of attempting to blow up a Tube train at Warren Street station. He was arrested in Birmingham. Under anti-terrorism legislation they have 14 days to interview them.
In Rome, Osman Hussain was reported by Italian newspapers to have told an investigating judge that the 21 July attacks were motivated by anger over Iraq, rather than religious reasons. He is also reported to have said the attacks were designed as a copycat of the 7 July bombings and aimed at frightening people.
He is said to have claimed he was not carrying enough explosives even to "harm people nearby". He is being held at Rome's high-security Regina Coeli prison. Two of his brothers have also been arrested by Italian police, one on Friday, and a second yesterday in Brescia, in the north.
Hussain is said to be prepared to fight extradition, which would be the first under the new fast-track procedure for terrorist suspects.
He left Britain by Eurostar on Tuesday last week, the day before police released a clear image of him on a bus heading towards south London and simultaneously raided a house in Stockwell where it was believed he lived. Three women there were arrested. The suspect was traced to France using mobile telephone intercepts, then tracked to Rome, where his brother ran an internet café.
Home Office officials were unable to say why Hussain was not apprehended despite precautions introduced after the 7 July attacks. Embarkation checks were scrapped in 1994 for travellers to the European Union and four years later for other countries. But they were reinstated for 10 days after the 7 July blasts and again after the failed 21 July attacks. They will remain for the foreseeable future.
Geoff Hoon, the Leader of the Commons, was asked yesterday about passport checks at Waterloo station. He said: "I understand that concern, and I am aware that the Home Office will be looking at that. Certainly in recent times there has been enhanced security for those leaving the country, as well as for those coming into the UK. It is something we must continue to look at very carefully."
The Home Office is developing an "e-borders" scheme, under which the records of passengers, both those heading for and those leaving Britain, are checked against international lists of terrorist suspects.
Two of the three women held on Wednesday in Stockwell remain in police hands and the third has been released on police bail until early September.
Also in custody in London are a man arrested in Stockwell on Friday, 22 July, and two men held in New Southgate on 24 and 25 July. Police also arrested another man in Finchley, north London, on Tuesday. They have been granted permission to question these men until 2 August.
A man held in Tulse Hill, south London, on 23 July was released without charge at the weekend as were two women held on Friday at Liverpool Street station in the City of London.Reuse content