All indications are it is the modus operandi of al Qaeda-type groups that typically involve planning and logistics operatives in the background. The attacks bear similarities to suspected al Qaeda bombings that killed 191 people on four rush-hour commuter trains in the Spanish capital Madrid last year, although those were not suicide blasts.
The head of the Metropolitan Police's anti-terrorism branch - Peter Clarke - said police were looking into the movements of the four men, three of whom were from the Leeds area.
|"We now know that all four of these men arrived in London by train on the morning of Thursday, July 7. We have identified CCTV [closed circuit television] footage showing the four men at King's Cross station shortly before 8:30 a.m. on that morning, July 7," he said.|
Twenty minutes later, three bombs went off within 50 seconds of each other on crowded subway trains. The fourth went off on the bus almost an hour later.
Security experts say the attacks show a level of planning and technical know-how that strongly suggests the four did not act alone, but were carrying out a carefully planned attack that involved a mastermind and a support network.
All four of the suspects appear to have lived normal lives. Neighbours of the men have expressed shock at the possibility that they could have been involved in the attacks.
News reports have identified three of the four suspects:
|"I would be surprised if this was something that was generated in someone's flat outside of London in a small Pakistani community," said former CIA official Nick Pratt, a terrorism expert at the Marshall European Center for Security Studies in Germany.|
"To be able to pull something like this off, to get a hold of the explosives, it strikes me as implausible that it would be just four singletons working by themselves."
"Clearly there will be people behind this group and involved in this and clearly we are seeking those people," a police spokesman said. "The assumption has got to be they weren't acting alone."
"The way I have seen these cells work, you have a logistics cell, you've got someone who deals with transportation, you've got a security cell ... The one thing that gets uncovered is the actual operator cell, the guys that pull the bombing off."