LONDON, JUNE 25 -- At least eight people were injured tonight when a bomb exploded at a social club in central London frequented by members of Britain's ruling Conservative Party.

Police blamed terrorists for the bombing attack on the 159-year-old Carlton Club and said it may have been the work of the outlawed Irish Republican Army. There was no immediate claim of responsibility.

A government minister said that if the IRA was responsible, it marked an important shift in the guerrilla group's tactics from military targets back to political ones. IRA members have carried out a wave of bomb and gunfire attacks against military facilities and personnel in Britain and Europe in recent months, but the last IRA attack on government figures was in 1984 when a bomb exploded at the hotel in Brighton where most of the government's ministers, including Prime Minister Margaret Thatcher, were staying.

The bomb at the Carlton Club contained 15 pounds of explosives and was placed several feet inside the front door, according to police. The blast rocked the club, which is near Trafalgar Square and a few hundred yards from Buckingham Palace, at about 8:30 p.m. (3:30 p.m. EDT) and could be heard in Parliament about a mile away.

Thatcher, a member of the club, was in Ireland at a summit of European Community leaders, but other Tory politicians were in the three-story building.

Among the injured was Lord Kaberry, 82, a former vice-chairman of the Conservative Party, and a former member of Parliament. He and four others were taken to Westminster Hospital for treatment. Fire officials said 24 people were rescued from the building.

Three other injured persons, all American, were taken to St. Thomas's Hospital suffering from cuts and shock. One, Jane Kahan, 49, of New York, who was treated for cuts, said she had just come out of Christie's auctioneers next door when she "heard a terrible crash and looked up and saw a window had blown out of the building nearby. Some of the fragments of glass hit me."

Another American, Jacob Boal-Teshuva, 61, of New York, came out of St. Thomas's with a bandaged leg after being hit by glass. "As we were walking toward St. James's Park, there was a huge explosion and smoke everywhere," he said.

Almost all Conservative prime ministers have been members of the club. Because it is an all-male club, Thatcher was made an honorary member when she became Conservative Party leader in 1975.

Last year, government ministers held a dinner at the club for Thatcher to mark her 10th anniversary as prime minister. Many Tory members of Parliament and ministers are members, and only those who are British citizens and accept the Conservative Party philosophy are allowed to join. The club has been the scene of many important events in Conservative Party history.

The head of the police anti-terrorist branch, Commander George Churchill-Coleman, said of the explosion in a reference to the IRA: "It brings a new dimension to the campaign, and I must warn the public in general that. . . everyone must be on their guard."