Police conducted raids in the south London suburbs of Stockwell and Clapham and said they had arrested two men “on suspicion of the commission, preparation or instigation of acts of terrorism.”
A police spokeswoman said the arrests were in connection with the failed bomb attacks of July 21.
With many Londoners fearful that attackers could hit the Underground and bus systems a third time, authorities are probing for any solid connections between the first two plots, which appeared similar on the surface.
The groups struck exactly two weeks apart and both hit three tube train carriages and a red double-decker bus.
The July 7 attacks killed 52 victims and all four suicide bombers, while the July 21 attackers’ explosives failed to detonate and took no lives.
Alex Standish, editor of Jane’s Intelligence Digest said it’s likely the two cells, the first made up mostly of Pakistani Britons and the second of immigrants from East Africa, did not know of one another but reported to the same organiser or bomb-making expert.
“If two groups like that could be set up by an outside individual or network, then the chances are there’ll be more than two groups. … There is absolutely no reason why a third, fourth, fifth cell shouldn’t exist,” Mr Standish said.
Interrogation of the captured July 21 suspects is unlikely to lead police to other cells, because terror networks’ vertical structure means those who carry out separate attacks have no knowledge of one another, he said.
In Italy, where one of the suspected July 21 attackers is being interrogated, Carlo De Stefano, head of the country’s anti-terror police, said the investigation so far indicated that the suspect,
Hamdi Issac, was “part of a loosely knit group rather than a well-structured group.”
Issac has been charged in Italy with association with the aim of international terrorism and possessing false documents, said Antonietta Sonnessa, his lawyer.
Italian police said his extradition to Britain would not take long.