The man shot and killed on a subway car by London [Images] police in front of horrified commuters apparently had nothing to do with this month's bombings on the city's transit system, police said Saturday in expressing their "regrets."

A day earlier, the police commissioner said the man was "directly linked" to Thursday's attacks, in which bombs on three subway trains and a bus failed to detonate properly. No one was injured.

"For somebody to lose their life in such circumstances is a tragedy and one that the Metropolitan Police Service regrets," a police spokesman said on customary condition of anonymity.

The man, whose identity has not been released, was shot Friday at a subway station in the south London neighborhood of Stockwell. Witnesses said the man appeared to be South Asian and was wearing a heavy padded coat when police chased him into a subway car, pinned him to the ground and shot him in the head and torso.

A spokesman for Scotland Yard said on customary condition of anonymity that the man was unconnected to the incidents of Thursday, in which bombs placed on three subway cars and a double-decker bus failed to detonate properly.

The spokesman also said the man was "probably unconnected" to the July 7 subway and bus bombings that killed 56 people, including four attackers.

However, Scotland Yard would not rule out that the man was not connected to any terrorist actions.

Hours after the man was killed, Metropolitan Police Commissioner Ian Blair said the shooting was "directly linked" to the investigations.

"The man who was shot was under police observation because he had emerged from a house that was itself under observation because it was linked to the investigation of yesterday's incidents," police said Friday.

"He was then followed by surveillance officers to the station. His clothing and his behavior at the station added to their suspicions."

Police investigating Thursday's attacks also said Saturday they had arrested a second man in the same south London neighborhood where the shooting occurred and another person was detained.

Thousands of officers fanned out in a huge manhunt amid hopes the publication of images of four suspected attackers would lead to their capture.

Security alerts kept the city of about 8 million on edge. Police briefly evacuated east London's Mile End subway station in one such incident and one witness reported the smell of something burning. Service was suspended on parts of two subway lines, but police said later the incident "turned out to be nothing."

The mourning continued, with hundreds packing Westminster Cathedral for the funeral Mass of Anthony Fatayi-Williams, a 26-year-old who was among the 52 people killed by four suicide bombers in the first wave of attacks on July 7.

"These present atrocities and Anthony's death have raised great emotions in us," Auxiliary Bishop of Westminster Alan Hopes told mourners. "We are angry, we are appalled and we are grieving. But as Christians we cannot yield to bitterness, we cannot yield to thoughts of revenge."

The Metropolitan Police said the second arrest late Friday was "in connection with our inquiries" into Thursday's attacks. The first suspect, whose identity also has not been released, was being questioned at a high-security London police station.

Police would not say whether the men arrested were among the four suspected of carrying bombs onto three subway trains and a bus Thursday. The bombs failed to detonate properly and no one was injured in the attacks, which echoed the much deadlier blasts two weeks earlier.

Police said they had a good response to Friday's release of the photos, taken from the British capital's ubiquitous closed-circuit surveillance cameras, which have proved a boon for investigators.

The closed-circuit TV images of the suspects stared from the front pages of British newspapers Saturday.

"Faces of the four bombers," said the Daily Telegraph.

"The Fugitives" said The Times.

The Daily Mail labeled them "Human Bombs."

One image shows a stocky man in a "New York" sweatshirt running through a station. Another depicts a man in a white baseball cap and a T-shirt adorned with palm trees. Two others are in dark clothes, slightly obscured by a poor camera angle.

These have been days of high tension, disruption and fear on the London Underground. The union for subway and bus drivers said workers would be justified in staying away from work if the government fails to take more precautions to make the operators safe.

"I think they're going to strike again," commuter Warren West, 27, said of the bombers. "I think they're doing to London what's happening in

Heavily armed officers patrolled with clear instructions to stop suicide bombers � if necessary, with a shot to the head.

"If you are dealing with someone who might be a suicide bomber, if they remain conscious, they could trigger plastic explosives or whatever device is on them," Mayor Ken Livingstone. "Therefore, overwhelmingly in these circumstances, it is going to be a shoot-to-kill policy."

Thursday's bombs contained homemade explosives that only partly detonated, police said, adding that the attacks bore resemblance to the July 7 attacks, also on three subway trains and a bus. It was not clear if the explosives were of the same type.

A statement posted Friday on an Islamic Web site in the name of an al-Qaida-linked group claimed responsibility for Thursday's attacks.

Authorities, however, were skeptical. The group, Abu Hafs al Masri Brigades, has also claimed responsibility for the July 7 bombings � as it did for the 2003 New York City blackout and many other events.

Complete coverage: the London blasts