Three men were arrested today in connection with the July 7 terrorist attacks in London, two of them as they were about to board a flight to Pakistan.

The two, aged 23 and 30, were arrested by officers from the Metropolitan Police Counter Terrorism Command at Manchester airport and the third man, aged 26, was arrested at a house in Leeds shortly after 4pm.

They were all arrested on suspicion of the commission, preparation, or instigation of acts of terrorism under the Terrorism Act 2000.

Searches are being carried out at five houses in the Beeston area of Leeds, where three of the 7/7 bombers were based at one time or another. Searches are also being carried out at a flat and a separate business premises in East London.

The five houses in Beeston are in Cardinal Road, Colwyn Road, Firth Mount, Tempest Road, and Rowland Place. The property being searched today in Colwyn Road is on the same street as the house where 22-year-old Shehzad Tanweer lived with his parents. He was responsible for killing seven commuters in the blast at Aldgate tube station.

The arrested men are being taken to a Central London police station where they will be kept in custody and will be interviewed by officers from the Met’s Counter Terrorism Command.

A Scotland Yard police spokesman said that it was “a pre-planned, intelligence-led operation involving the MPS Counter Terrorism Command and the West Yorkshire Police Counter Terrorism Unit. “Armed officers were not used in the operation.”

Since the suicide attacks, when 52 people were murdered, police have been tracing the backgrounds of the bombers and trying to find out who funded and supported them and have pursued many lines of inquiry in the UK and overseas.

The spokesman added: “This remains a painstaking investigation with a substantial amount of information being analysed and investigated.

“As we have said previously, we are determined to follow the evidence wherever it takes us to identify any other person who may have been involved, in any way, in the terrorist attacks.

“We need to know who else, apart from the bombers, knew what they were planning. Did anyone encourage them? Did anyone help them with money, or accommodation?”

The investigation into the 7/7 attacks, codenamed Operation Theseus, has remained active both in the UK and abroad despite the lapse of time since the incidents.

It is understood that the Counterterrorism Command has been able to devote more resources to it recently after a lull in terrorist activity in the UK that followed the disruption of a major recruitment and training network.

Officers have been following up definite leads at home and overseas with a particular focus on who helped the leaders of the bomb cell - Mohammed Sidique Khan and Tanweer - in their planning and travel to Pakistan prior to the attacks.

A senior counter-terrorism source said: "We have never believed that it was possible for the four bombers to have done this entirely on their own. Other people must have known what they were doing and helped them in various ways."

It is now accepted among those investigating 7/7 and other terrorist operations that conclusions reached by the Intelligence & Security Committee last year were hurried and incomplete. Increasingly investigators are of the view that the 7/7 attacks were conceived of, planned in and directed from Pakistan where the leadership of al-Qaeda remains intact.

Lord Carlile, the Government’s watchdog on terror, told BBC News 24 the arrests were a “development” but that he hoped police had “got it right”.

The peer added that it was “wrong” to think the four bombers had been working alone and police had always been looking for others involved in the attacks.

He said: “Anybody who imagined that this had simply been treated as four lone wolves, or a lone pack of wolves on July 7 2005, is very wrong. There is a lot of work going on.

“It is clear to me from my contacts as independent reviewer with police and other control authorities that a rigorous hunt is going on for everyone connected to the 7/7 attacks and that nobody involved in those attacks can lie easy in their beds without expecting police to turn up one day and arrest them for very, very serious crimes.

“As to whether the people arrested today are involved, that is a matter for a decision by a court. I know nothing about them at this stage.”

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