BRITISH POLICE DETONATE BOMB; IRA SUSPECTED.

Byline: Sarah Lyall The New York Times

Responding to telephone warnings that used Irish Republican Army code words, the police destroyed a bomb that had been left Thursday in a telephone booth in the heart of London's crowded West End.

The incident came less than a week after the IRA declared an end to its 17-month cease-fire and set off a 500-pound bomb in East London, killing two people and causing an estimated $230 million in damage.

Experts said Thursday's bomb scare was a clear sign that last week's explosion was not an isolated incident, and that the IRA was prepared to return to its policy of sustained terrorist attacks in London.

No one was hurt by Thursday's bomb, which was destroyed in a controlled explosion as it lay in a gym bag in a telephone booth at 67 Charing Cross Road, near the Leicester Square tube station. It was described as "small" - containing possibly just a pound or so of Semtex explosive. But with a square-mile section of the city shut down for almost four hours Thursday afternoon, the incident succeeded in crippling the heart of London and sending a shiver of fear through pedestrians and office workers.

In an interview Thursday morning in An Phoblacht, the weekly newspaper of Sinn Fein, the IRA's political arm, an IRA official was quoted as saying that the group had no plans to resume the cease-fire.

The IRA, which wants an end to British rule in the province of Northern Ireland, "will continue to assert Irish national rights in the face of British denial for as long as is necessary," the official said.

The IRA, with its return to a campaign of huge attacks followed by smaller but highly disruptive ones, appears to be pursuing a delicate and potentially risky strategy. While this strategy minimizes casualties, it creates enormous disruption and inconvenience to the city and fear and pressure among the people.

According to the Metropolitan Police, it was a pair of telephone calls about 12:30 p.m. that raised the alarm. The calls fit the pattern of previous IRA attacks, with the callers using code words known to the group and to the authorities. The codes are simple - a name, a special word, a color - and are meant to signal that the call is not a hoax or the work of a lone terrorist.

Because the calls were vague about where the bomb was planted, the police were forced to block off a wide swath of central London, in the heart of the city's theater, shopping and tourist districts - from Pall Mall in the south to Oxford Street in the north, and from Park Lane in the west to Charing Cross Road in the east. Pedestrians were evacuated, traffic was diverted, subway stations were closed, and residents and office workers in the area were ordered to stay indoors and keep away from windows.

At the Porcupine Pub, just across the street from the site of the bomb, officials told the workers and customers to get as far away from the glass windows as they could. In last week's explosion, most of the injuries were caused when windows shattered, spraying glass onto office workers and passers-by.

"We took everybody straight to the cellars," John Burton, a bartender, told a local news station.

After they destroyed the bomb, using a remote control robot, the police said it had "all the hallmarks" of an IRA device.