British police Wednesday said they arrested one of the four alleged terrorists who botched an attack on London's transit system on July 21.

Officers with Scotland Yard (search) staged an early morning raid in Birmingham, arresting Yasin Hassan Omar (search) and three other men.

Officers zapped Omar with a taser gun to subdue him, Sky News reported. He was taken to the high-security facility at London's Paddington Green police station (search) for questioning.

Also Wednesday, Scotland Yard released a photo of another man they're seeking in connection with the July 21 attacks.

Elsewhere, off-duty British police nabbed two men traveling on a train in England's Western Midlands region. Lincolnshire police said the train, which was on its way to London's King's Cross station from Newcastle, was stopped at Grantham where the men were arrested late Tuesday.

In addition, police arrested a man at Luton's airport near London under anti-terrorism legislation as he prepared to leave on a flight for France, authorities said. Police did not say why he was arrested or if it was connected with the recent London attacks.

Authorities in Britain have been trying to find the people who planted four bombs on London Underground trains and a bus on July 21, but failed to fully detonate. The attempted attack came two weeks after four explosions ripped through three trains and a bus on July 7, killing 56 people — including the four homicide bombers.

Police have also been trying to determine whether the failed bombings and the July 7 attacks are connected.

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Explosives specialists were called to the scene of the Birmingham arrest to investigate a suspicious package. One hundred homes in the Hays Mills area of Birmingham were evacuated while the package was disposed of in a controlled explosion.

Besides Omar, the three other arrests in Birmingham and the two in the Western Midlands were being described as "peripheral," but related to the investigation. The Birmingham trio were heing held in custody in the city; it is unclear where the other two men were being held.

The arrests came as explosives experts were examining suspicious material found in a north London apartment connected to two men suspected of planting failed bombs, both identified as African immigrants who moved to Britain as children.

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

On Tuesday, Prime Minister Tony Blair said his government was determined to press forward with new anti-terrorism legislation in the wake of the attacks and vowed not to "give one inch" on his policies in Iraq or the Middle East.

Blair on Wednesday declined to comment directly on the arrests but paid tribute to the British police.

"I would just like to say that over these past couple of weeks the police have performed in an astonishing way. Their dedication, their commitment, their energy in getting after the people responsible has been remarkable," Blair said.

He said international governments needed to improve the way they cooperated in their fight against terrorism.

"There will be a strong statement, I hope, coming out of the United Nations Millennium summit in September on this," Blair said.

Polls suggest a majority of Britons share that view and that among Muslims, according to a poll released Tuesday, 79 percent believe Iraq was a factor in the attacks.

At least one witness to the raid said Omar appeared to be one of the four men arrested.

"I looked out of the window and the road was full of armed police and they had got the road closed off," said electrician Andy Wilkinson, who lives nearby.

"After 10 or 15 minutes, they brought a guy out. He looked like the darkest-skinned one in the photos of the four suspects released by the police — the one with the curly hair," Wilkinson said. "They had him dressed in one of those white suits. He had plastic cuffs on the front."

Omar arrived in Britain from Somalia in 1992 at age 11, the Home Office said. The 24-year-old, a Somali citizen with British residency, is suspected of attempting to blow up a subway train near Warren Street station.

Authorities released Omar's name on Monday when they said he and Muktar Said Ibrahim, 27, also known as Muktar Mohammed Said, were two of the four men suspected of planting last week's bombs.

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.

Both Omar and Said are the children of refugees, the government said.

According to Britain's Press Association, Said was part of a gang that carried out a series of muggings in the mid-1990s. He was sentenced to five years imprisonment in early 1996 but qualified for early release in 1998 after serving 2 1/2 years.

Press Association said that when he was released, Said grew a beard, adopted Islamic dress and became very devout. Police are looking into whether he attended the Finsbury Park or Brixton mosques in London, once considered magnets for radical Islamic clerics, and are investigating whether he met shoe-bomber Richard Reid, Press Association said.

Reid, who failed in his 2001 attempt to blow up an airplane, is serving a sentence of life imprisonment in the United States.

The Birmingham arrests also came as police explosives experts were examining suspicious material found in a north London apartment connected to two Omar and Said.

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

The Birmingham arrests would bring the number of people that police have said are being held in connection with the July 21 bombings to nine. Police last week arrested and were questioning five other people in relation to the botched bombings. It remained unclear if the other two being held had anything to do with the attacks.

The Associated Press and Sky News contributed to this report.