LONDON, FEB. 18 -- A terrorist bomb exploded at crowded Victoria railway station during the peak of the morning rush hour today, killing one commuter and injuring at least 41 other people.

Three hours earlier a bomb exploded at Paddington railway station, but the facility was nearly deserted, and no one was injured.

The outlawed Irish Republican Army, which is attempting to force an end to British rule of Northern Ireland, claimed responsibility late tonight for both explosions and said in a statement that the casualties resulted because authorities failed to evacuate city railway stations after a warning telephone call.

All four terminals at Heathrow, the country's largest international airport, were closed this afternoon for an hour and a half after an anonymous bomb warning apparently unconnected to the earlier bombings, but no explosives were found. Departing flights were held up, while incoming planes were kept on runways with their passengers still aboard.

Eleven days ago the IRA fired homemade mortar shells at the Downing Street residence of Prime Minister John Major, narrowly missing him and cabinet colleagues.

Today, police said, a man with an Irish accent phoned a travel information center 40 minutes before the Victoria station explosion, saying, "We are the Irish Republican Army" and warning that all of the city's 11 main-line rail stations would be hit.

Police began searches, but did not immediately close the stations. They said later they had received a number of unfounded bomb calls and considered this one too vague. Tonight's IRA statement said, "All future warnings should be acted upon."

Within minutes of the blast, police sealed off all 11 stations, setting off a chaotic scramble for alternative ways into town for about a half-million rail commuters. The bomb was placed in a trash can in the main hall of the station near a self-service ticket machine and a row of pay phones, authorities said. It went off about 7:40 a.m. as commuters were crowded around the machine to buy tickets.

"There was a big blinding light, a wall of fire, followed by a noise which came towards me," said Matthew Cyprus, 22, an assistant store manager, whose right foot was injured. "People were shouting, 'Get out as quickly as you can.' There was screaming and panic."

Bus driver Jay Patel, who had just pulled up to the front of the station, told reporters: "People were running out of the station covered with blood, with their clothes torn. I saw a woman, her face covered with blood, run out of the station towards a policeman. Then her legs buckled, and she fell to the ground."

The dead man was not identified. Two of the injured were reported to be in critical condition.

George Churchill-Coleman, commander of Scotland Yard's anti-terrorist squad, called the bombing "a totally indiscriminate and vicious act on the traveling public carried out at a time when the perpetrators knew perfectly well Victoria Station would be crowded with commuters."

The last IRA attack to cause serious casualties on the British mainland was the December 1983 bombing of Harrods department store, in which six people were killed. Last year, IRA bombs damaged the London Stock Exchange and the Carlton Club, which is patronized by leaders of the ruling Conservative Party.

Home Secretary Kenneth Baker, who is in charge of police affairs, said he was "disgusted and appalled" by today's attack, which he said was "quite cruelly calculated to do the greatest damage to innocent men, women and children."