London bomb suspect arrested Three women arrested suspected of 'harboring offenders' Police on Wednesday released this photo of a man wanted in connection with the bombing attempts. RELATED SPECIAL REPORT YOUR E-MAIL ALERTS Acts of terror London or or Create Your Own LONDON, England (CNN) -- Police on Wednesday arrested one of the four men they believe responsible for last week's attempted bombings of London's mass transit system, the head of Britain's anti-terror police branch said. Yasin Hassan Omar, a 24-year-old Somali with British residency, was arrested early Wednesday morning in Birmingham, England's second largest city about 160 kilometers (100 miles) north of London. Police allege that Omar, 24, was the would-be bomber of the city's Warren Street Underground station. Omar, who was alone, resisted arrest and was subdued after police used a Taser "stun gun," said Peter Clarke, head of the Metropolitan Police Anti-Terrorist Branch. No gunshots were fired, police said. Three other men were arrested elsewhere in Birmingham around the same time at 4:30 a.m. (11:30 p.m. ET Tuesday), police said. "This, of course, is an important development in the investigation," Clarke said. "However, I must stress how important it is for the public to remain watchful and alert. We are still looking for the other three men whose pictures we released," Clarke said, referring to the other suspected bombers. Wednesday night, police released a new picture of another of the suspected bombers. He is believed to have tried to set off a device at Shepherd's Bush Underground station. He and the would-be bomber of the city's Oval Station have not yet been identified by police. Clarke said a previously released picture of the Shepherd's Bush suspect was taken at Westbourne Park Underground station. In it, he is wearing a dark blue short-sleeve England soccer shirt and dark trousers. Police said they believe that after running from that station, he threw the shirt away on McFarlane Road near Wood Lane about 12:30 p.m. The latest picture shows him on a No. 220 bus wearing a white tank top with dark trousers. Police believe he got on the bus on Wood Lane about 1:20 p.m. and stayed until the end of the route at Mapleton Road-Wandsworth, Clarke said. He got off the bus at 2:07 p.m. near Garratt Lane, close to the Arndale Centre. "We need to know where he went when he got off the bus," Clarke said. "Until these men are arrested, they remain a threat," he said. When shown the image on a laptop computer, several neighbors of an apartment in Stockwell raided by police Wednesday night said they recognized the man in the tank top. "I'm 100 percent sure, 110 percent," one man told CNN. During the search of the ground-floor apartment in the Stockwell neighborhood, police arrested three woman on suspicion of "harboring offenders" in connection with the July 21 attempted bombings. They were taken to a police station in central London, where they remained in custody, Scotland Yard said. The raid in South London was near the Stockwell Underground station where three of the four bombers boarded their trains. Omar a resident since 1992 A nationwide manhunt has been under way since the July 21 partial detonations of backpack bombs in London. The attacks were similar to those on July 7 that killed 52 commuters and the four bombers. Both attacks targeted three underground trains and a double-decker bus. In closed-circuit television images from July 21 that were released by police, Omar is wearing a blue shirt as he jumps the turnstile to flee the Warren Street station, minutes after the backpack bomb failed to fully detonate. Omar came from Somalia in 1992 and is a legal permanent resident of Britain, the Home Office said. Although intelligence suggested that no explosives were in the house where Omar was arrested, about 100 nearby homes were evacuated as a precaution, Clarke said. Andy Wilkinson, a neighborhood resident, told the UK's Press Association he saw a dark-skinned man with curly hair being led away from a nearby residence in a white forensic suit and plastic handcuffs. "It was about 10 past five and all we could hear was a right racket -- people trying to break a door down," Wilkinson said. "I looked out of the window and the road was full of armed police and they had got the road closed off." Omar was taken to the high-security Paddington Green police station in London. The three other men were arrested more than three kilometers (two miles) away. They were held in a local police station. Police said Wednesday that one of five men previously arrested in London since July 21 -- none of them identified as key suspects -- had been released from Paddington Green. He was picked up Friday in a raid in Stockwell. The other four men were also detained after a series of raids across London in the days after Thursday's incidents. British Prime Minister Tony Blair said he was "greatly heartened" by the arrests in Birmingham, which he called "an important development." Eritrean suspect identified In addition to Omar, police have identified one other suspected bomber, Muktar Said Ibrahim. Ibrahim's family in London provided police with information that led to his identification and called on fellow citizens to do the same. Ibrahim, 27, arrived from Eritrea in 1990, and became a British citizen in 2003, according to the Home Office. He is suspected of targeting a double-decker bus in the city's East End. Residents of a north London building apartment raided Monday by Metropolitan Police said Omar and Ibrahim lived together. The raided apartment has been registered for the past six years to Omar, who until recently received a $550 monthly housing subsidy from the government. Anti-terrorist officers also searched and conducted forensic examinations at two other residences in north London Wednesday, according to a police statement. There were no arrests. One of the residences is in the same neighborhood where police Tuesday impounded a white Volkswagen as part of the July 21 probe. Metropolitan Police Commissioner Ian Blair said Tuesday the July 21 bombs, which failed to explode, were just as powerful as the July 7 ones, but there was "no direct link at the moment" between the two groups of attackers. The July 7 bombings were carried out by three British-born Muslims of Pakistani heritage who hailed from the city of Leeds, about a three-hour drive north of London, and a fourth British citizen, a Muslim convert of Jamaican birth who lived closer to London. Three of the July 7 bombers traveled to the city from Luton in north London, and five days later police found more than a dozen unexploded bombs in a car at the Luton train station, two sources familiar with the investigation told CNN. (Full story) CNN's Nic Robertson, Henry Schuster, Phil Hirschkorn and Andrew Carey contributed to this report. Home Page Get up-to-the minute news from CNN CNN.com gives you the latest stories and video from the around the world, with in-depth coverage of U.S. news, politics, entertainment, health, crime, tech and more. Home Page Get up-to-the minute news from CNN CNN.com gives you the latest stories and video from the around the world, with in-depth coverage of U.S. news, politics, entertainment, health, crime, tech and more.