The man shot dead by police in front of terrified passengers inside a subway car Friday was an innocent Brazilian bystander mistaken for a suspect in the abortive bomb attacks the day before, police officials acknowledged Saturday.

The officials said the man emerged from the same South London apartment complex as a prime suspect in the failed bombings of three subway trains and a double-decker bus, and was followed by armed plainclothes officers to a nearby subway station.

They gave chase fearing the man was preparing to attack a train, police officials said. The officers pushed him to the floor of the car and shot him five times in the head at close range, according to witnesses, who gave searing accounts broadcast on television and radio. Under guidelines adopted in recent years, officers are advised to shoot suspected suicide bombers in the head to prevent them from setting off explosives.

Police identified the man as Jean Charles de Menezes, 27, a Brazilian citizen.

The mistaken shooting set off a new wave of alarm and criticism from leaders of Britain's minority Muslim community, who expressed concern that police are singling out men with certain physical characteristics or ethnic backgrounds in their pursuit of the would-be bombers, believed to be Muslims of South Asian or North African origin.

"We accept that police are under tremendous pressure to apprehend the criminals attempting to cause carnage, but we believe this incident makes it vital that the authorities explain and follow the rules of engagement to ensure innocent people are not caught up and killed due to overzealous policing," said Inayat Bunglawala, spokesman for the Muslim Council of Britain.

A police statement expressed regrets for the killing and added: "For somebody to lose their life in such circumstances is a tragedy." Officials said the incident would receive a full investigation but declined to comment further.

In Brazil, the Foreign Ministry said it was "shocked and perplexed" by the death of Menezes, whom it did not name but described as "apparently the victim of a lamentable mistake," the Associated Press reported.

The ministry said it expected British authorities to explain the circumstances of the shooting, and Foreign Minister Celso Amorim would try to meet with British Foreign Secretary Jack Straw during a visit to London.

Meanwhile, police questioned two men arrested Friday in south London under anti-terrorism laws, while investigators combed this anxious city for the four men suspected of carrying out the failed bomb attacks. The small explosions killed no one but were attempted carbon copies of the July 7 suicide bombings during morning rush hour here that killed at least 56 people -- including the four suspected bombers -- and injured 700.

The two men were held after raids late Friday in the Stockwell area, near the station where Friday's fatal shooting occurred. The site is one stop south of Oval station, which was the site of one of the failed attacks Thursday.

Bunglawala said the police force needed to convince anxious Muslims and other minority groups that it was concerned for their safety. At the same time, he said, Muslims must help the police catch the would-be bombers.

"We've all seen the four images -- surely their brothers, sisters, parents and friends must know who these people are," he said.

Officers had staked out a number of potential suspects and locations after the bombing attempts in hopes of catching the assailants. One site was an apartment complex in Tulse Hill, near Stockwell, an ethnically mixed blue-collar neighborhood.

The man who emerged Friday morning was wearing a padded, blue-fleeced jacked and dark baseball cap that covered his features and made him appear suspicious as well as harder to identify, police officials said. Officers from a specialist undercover firearms unit trailed him as he took a bus to the Stockwell station. As he headed into the station, the officers bolted after him, and the man ran toward the platform, witnesses said. He stumbled into a subway car and three undercover operatives with handguns piled on top of him. One opened fire, according to witnesses, who gave graphic accounts of what one newspaper termed "an execution."

Ian Blair, commissioner of the Metropolitan Police, said Friday that the man was linked to the probe into the abortive bombings. He also told reporters that officers had ordered the man to halt and had opened fire only after he failed to obey. But none of the witnesses reported hearing any warning.

The shooting took place under shoot-to-kill guidelines adopted after the Sept. 11, 2001, attacks in the United States under the name "Operation Kratos" to deal with the threat of suicide bombers. While officials would not publicly discuss the guidelines, sources told British reporters that a senior officer is authorized to deploy special armed units to track and, if necessary, shoot dead suspected suicide bombers. The officers are advised to shoot such assailants in the head to keep them from setting off explosives.

The guidelines are based in part on procedures used by the Israeli authorities in intercepting suicide bombers. But police officials insist officers still must follow the law, which only allows the use of reasonable force in preventing a crime. The guidelines of the Association of Chief Police Officers say police should not open fire except when someone's life is in danger and there is no other way to stop the assailant.

The shooting of the wrong man fueled the sense of unease that has gripped London since the bomb attacks Thursday.

Meanwhile, a 17-year-old boy was remanded in custody, charged with an arson attack on the home of Germaine Lindsay, whom police alleged was one of the London suicide bombers.

Jean Charles de Menezes, 27, was an electrician.