LONDON — Police investigating the failed July 21 bomb attacks in London said yesterday they had arrested two men in city raids, as authorities tried to determine whether there were links between that attack and the transit bombings two weeks earlier.

A total of 23 people have been arrested in connection with the failed bombing attempt, including the four main bombing suspects in police custody in London and Rome.

British transport police, meanwhile, dispatched reinforcements from around the country yesterday to patrol London's subway system in a show of force meant to discourage more attacks.

The July 21 bombing attempt came exactly two weeks after the July 7 attacks that killed 52 people plus all four suicide bombers. Both attacks hit three subway cars and a red double-decker bus, but the July 21 attackers' explosives failed to detonate and took no lives.

The men in the arrests announced yesterday have been detained "on suspicion of the commission, preparation or instigation of acts of terrorism," a Metropolitan Police spokeswoman said. They were arrested after searches of three properties in the Stockwell and Clapham areas of south London.

With many Londoners fearful of a third round of attacks on the Underground and bus systems, authorities looked for any solid links between the first two plots, which appeared similar on the surface.

"There is a resonance here," Metropolitan Police Commissioner Ian Blair noted hours after the second round of attacks.

It's likely the two cells — the first made up mostly of Pakistani Britons and the second of immigrants from East Africa — didn't know of one another but reported to the same organizer or bomb-making expert, said Alex Standish, editor of Jane's Intelligence Digest.

"That has to be the assumption [investigators] are working on at the moment," he said. "Only by uncovering the structure can they hope to discover whether there are further cells operating in the U.K. There is absolutely no reason why a third, fourth, fifth cell shouldn't exist."

But, he added, interrogation of the captured July 21 suspects is unlikely to lead police to other cells, because terror networks are set up so that those who carry out separate attacks have no knowledge of one another.

In Italy, Carlo De Stefano, head of anti-terror police, said the investigation so far indicated that Hamdi Issac, one of the suspected July 21 attackers held in Italy, was "part of a loosely knit group rather than a well-structured group."

Issac was charged in Italy yesterday with association with the aim of international terrorism and possessing false documents, said Antonietta Sonnessa, his lawyer. Italian police said his extradition to Britain wouldn't take long.

Italian media have reported that Issac told police his group was not linked to either the July 7 bombers or the al-Qaida network.

Sonnessa told Britain's ITV News that Issac claimed the July 21 plot was put together the day before, "in a meeting with this group of friends."

In another matter, British police visited the family of a Brazilian electrician, who was shot dead in London by officers who mistook him for a suicide bomber, to apologize yesterday and discuss compensation for the killing.

Jean Charles de Menezes, 27, was shot eight times by plainclothes policemen on July 22 at a London underground station.

British newspapers said police could offer the family up to $1 million in damages.

Egyptian police kill

bombing suspect

CAIRO, Egypt — Egyptian police cornered a main suspect in last month's Sharm el-Sheik bombings in his mountain hideout yesterday and killed him in a shootout that also fatally wounded his wife, authorities said.

A police official said the couple's 4-year-old daughter was wounded.

Police hunting Mohammed Saleh Flayfil, 30, a Bedouin also wanted in last year's bomb attacks at the Taba resorts in the Sinai, found the family hiding in a quarry in Mount Ataqaa, 17 miles east of the Cairo-Suez highway, the Interior Ministry said.

Flayfil was being tried in absentia for the bombings in Taba in October that killed 34 people and was a main suspect in the Sharm el-Sheik attacks of July 23 that killed at least 64 people.