Police stormed a brown-brick duplex Wednesday and used a stun gun to arrest a Somali suspected of being one of four men behind botched attacks in London — a breakthrough that could yield the inside story on terror bombings that set the British capital on edge.

Yasin Hassan Omar (search), 24, was carted to a top-security police station in London, and a key official called the arrest significant — but warned that until all the bombers were in custody, the threat remained.

Dozens of anti-terrorist police and bomb disposal experts, some in heavy body armor, swept into a neighborhood of Britain's second-largest city to arrest Omar, a Somali citizen with British residency who is suspected in the botched July 21 attack on the Warren Street subway station.

"They had him dressed in one of those white suits. He had plastic cuffs on the front," said one neighbor, Andy Wilkinson, who recognized Omar from police images of suspects. Police use such suits to preserve physical evidence that may be on a suspect.

Police also detained three other men at a house about two miles away, saying the arrests were linked to the second set of failed bombings, but declining further comment. In all, eleven suspects are being held, though only Omar is thought to be one of the bombers, police said.

Interrogations of Omar may be key to determining whether the second set of bombings July 21 are linked to the July 7 attacks that killed 56 people, including the four bombers.

After arresting Omar, police evacuated up to 100 homes and sent a bomb squad into the Small Heath neighborhood (search) in Birmingham, a city some 120 miles northwest of London.

They allowed a few residents to pick up belongings during the day, but kept up cordons near Omar's rundown house next to a sprawling park. The blue-framed door was ajar as investigators moved back and forth between the home and a white police trailer parked out front.

Kati Stewart, 31, a health care worker who lives across the street from Omar, said she'd seen four men coming and going frequently over the past two weeks. "They would come at 2 a.m., and then when you looked in the morning, the car had gone," she said.

But Omar generally attracted little attention in the diverse neighborhood, where residents of many ethnic backgrounds and faiths — Indian, Pakistani and Irish; Christian, Hindu and Muslim — say they live together peacefully.

One woman said she believed Omar had lived in the close-knit area for less than a year. "Everybody knew that he didn't interact with the neighbors much at all," said the 38-year-old neighbor, who would give her name only as Anna.

Other raids were carried out Wednesday in south London's Stockwell district (search), where officers arrested three women on suspicion of "harboring offenders," and on two more London homes, where no arrests were made but forensic tests were conducted, police said.

Police were still seeking three other men believed involved in the failed bombing attempts.

"I must emphasize that until these men are arrested, they remain a threat," said Peter Clarke, the head of London's police anti-terrorist unit, though he called Omar's arrest "an important development in the investigation."

Police also released another photograph of a suspect who tried to detonate a bomb on a train near the Shepherd's Bush subway station. The man took off a blue T-shirt after the attempted bombing, changed into a white sleeveless shirt and jumped on a bus he rode until the end of the line.

Prime Minister Tony Blair (search) appealed for greater international cooperation in the fight against terrorism and urged the United Nations to make a strong statement on the issue. A succession of world leaders praised Blair's resolute response to the July 7 attacks on London's transit system.

The world must not allow "the terrorists to divide us by nation or by race or by religion," said Blair.

The failed bombs planted were stored in clear plastic food containers and put into dark-colored bags or backpacks. Police said the bombs were similar to another found abandoned in a park Saturday, raising fears that a fifth bomber was on the loose.

Of the four men suspected of planting the explosives July 21, police have identified two — Omar and Muktar Said Ibrahim, 27, also known as Muktar Mohammed Said. Both are children of refugees, the government said.

Omar arrived from Somalia in 1992. Said came to Britain in 1990 from Eritrea, his family said. He was granted residency in 1992 and British citizenship in September 2004, the Home Office said.

Said was part of a gang that carried out a series of muggings in the mid-1990s but qualified for early release in 1998, the British news agency Press Association reported. When he left prison, Said had a beard, had adopted Islamic dress and was very devout, Press Association said.

Police are also looking into whether Said attended the Finsbury Park or Brixton mosques in London, once considered magnets for radical Islamic clerics, and whether he met shoe-bomber Richard Reid, who is serving a life sentence in a U.S. prison after a failed attempt in 2001 to blow up an airplane, the news agency said.

Explosives experts were also examining suspicious material found in a north London apartment connected to both Omar and Said.