LONDON — Police SWAT teams captured the final three fugitives wanted for trying to bomb the London transit system yesterday, two in a dramatic raid on a public-housing project here and the third seized by Italian police who tracked him to an immigrant suburb of Rome.

The capture of the men, whose images were filmed by security cameras and shown repeatedly during the manhunt, left Londoners feeling considerably safer. But British police warned there was much work left to be done. The investigation now shifts to identifying suspected planners, bomb-makers and accomplices in Britain, Italy and elsewhere.

"There will be more very visible police activity," said Peter Clarke, who leads anti-terror operations for London's Metropolitan police.

It seemed clear that police had closed in on the fugitives based on evidence gathered in 13 previous arrests, particularly the capture of the fourth suspect in Birmingham, England, on Wednesday. Phone intercepts were also important, investigators said.

The arrests culminated a manhunt that spanned at least three countries and began after bombs failed to explode on three subway cars and a bus July 21. The attacks came two weeks after four similar attacks that killed 56 people.

During a raid yesterday morning on a top-floor apartment of a public-housing project in London's Notting Hill neighborhood, a police SWAT team captured Muktar Said Ibrahim, who a fellow suspect told police was the leader of the four bombers. Said was arrested along with Ramzi Mohammed, an athletic-looking young man who had been filmed wearing a New York sweat shirt as he fled commuters who tried to tackle him after the attempted bombing of a train at the Oval station.

Officers in helmets, gas masks and body armor charged across a balcony firing tear gas into the apartment. Shortly afterward, Said and Mohammed appeared shirtless on the balcony, with hands up, and disoriented, as police trained guns on them. They were led away wearing hooded suits used to preserve evidence.

In Rome, police captured the fourth accused bomber, identified as Hussain Osman, 27, a Briton of Ethiopian descent who once lived in Italy, a senior Italian anti-terror official said. The official described the name Hussain Osman as an alias that the suspect used when he posed as a Somali refugee to gain legal residency in Britain.

The official said Osman's real first name is Isaac, and that he was hiding at his brother's apartment in a neighborhood populated by immigrants from Ethiopia, Eritrea and Somalia.

Osman fled Britain after hiding there for three or four days, but not before British police managed to detect and monitor a cellphone he was using, Italian officials said.

Although the fugitive changed phone cards and took other precautions as he traveled by train, investigators set up electronic surveillance and also shadowed the people he called. His cellphone activity allowed police to track him to Paris, Milan, Bologna and Rome, where he arrived two or three days ago, officials said.

Osman confessed to Italian police yesterday evening, the senior anti-terror official said, but the suspect made claims that investigators will have to evaluate carefully.

Intent to scare, not kill?

He asserted that the partial detonations on three trains and a bus July 21 were planned to inflict terror but not to kill anyone, the official said. And he insisted there was no connection between his London-based group and the suspected suicide bombers who struck two weeks earlier.

Instead, Osman claimed his London-based group seized the opportunity to put together a plot emulating the July 7 group, three of whom were from the northern city of Leeds.

"He said they did it inspired by the moment," the official said. "They wanted to defy the police with a demonstrative act. He says he knew very well they would be arrested."

But investigators find it difficult to believe that the backpack bombs were prepared with anything but lethal intent. If the bomb-maker had not made a mistake with the potent, homemade brew, the casualties would have had least matched the carnage on July 7, British police say.

Although the similar bombs, targets and methods make a link between the two plots likely, police have yet to find definitive evidence connecting them, investigators said.

Osman described the July 21 attack as the work of a tightly knit group of East African immigrants, the senior anti-terror official said. Osman was radicalized after arriving in Britain about five years ago, according to an Italian official.

Osman told interrogators that he and his fellow suspects attended the Finsbury Park mosque, a multiethnic hotbed of extremism in North London not far from the apartment shared by Said and accused bomber Yasin Hassan Omar, the Somali refugee captured in Birmingham on Wednesday. Osman told police that Said was the recruiter, bomb-maker and leader of the cell.

Police and court records depict Said, 27, a Briton who emigrated from Eritrea when he was 14, as the angry product of a London underworld where street crime and Islamic extremism converge.

After being convicted of robbery at 18, Said converted to Islam while serving a five-year term in several different prisons. He embraced radical Islam at the same prison where Richard Reid, who was convicted in the United States of trying to blow up a Paris-Miami flight, first fell under the spell of militants such as Abu Hamza al-Mazri of the Finsbury Park mosque, according to officials and court records.

The Italian official said Osman told police Said recruited the others partly during workout sessions at a gym, a pattern familiar from previous cases in which militants have bonded while practicing martial arts or sports.

"Of course, there is a lot of work to do to check out this story," the official said. "Among other things, he made a lot of phone calls to a lot of people in Britain and Italy who have to be traced and investigated. And their contacts have to be investigated."

Caught on camera

Security cameras caught Osman on the day he tried to ignite a backpack bomb in a train near the Shepherd Bush station. And an eyewitness description of Osman's demeanor just after the partial detonation raises questions about his claim in Rome that he did not intend to die on the train.

The detonation knocked him to the floor and left him groggy, the witness told several British newspapers. Osman then got up, climbed onto the tracks and escaped on foot, according to police.

His flight ended yesterday in Tor Pignatta, a working-class suburb on Rome's eastern edge, when teams of counterterrorism and SWAT police burst in using keys his brother provided, an Italian police official said. Osman did not attempt to flee or resist, police said.

The brother told police he had obtained false documents for the suspected bomber, suggesting that Osman was either going to keep running or establish himself somewhere else.

Early today, follow-up raids were being carried out in Milan, Brescia and Rome at the homes or properties of relatives or associates of Hussein, law-enforcement sources said.

As in Rome, the arrests in Britain reinforced the idea that the fugitives had taken refuge with relatives or friends in their ethnic communities. British police also arrested three other people yesterday, including one who is thought to be the brother of Mohammed, one of the bombers captured in the Notting Hill raid.

The arrests appear to give British police a rare prize: a full cell of alleged terrorists captured alive and unharmed, who could be questioned about possible links between their abortive attacks and the July 7 bombings.

Los Angeles Times writers Tracy Wilkinson and Livia Borghese contributed to this report, which was supplemented by The Washington Post.