IRA Says It Bombed Exclusive London Club : Terrorism: The British government sees the attack as a warning that civilians will not be spared.

The Irish Republican Army claimed responsibility Tuesday for the powerful bomb that shattered the ruling Conservative Party’s exclusive Carlton Club in central London the night before, and Prime Minister Margaret Thatcher’s government warned that the largely symbolic attack was a warning that civilians no longer will be spared in the group’s militant campaign for a united Ireland.

“This apparent change of tactics requires renewed vigilance on the part of everyone,” David Waddington, Britain’s home secretary, told Parliament as the two most seriously wounded victims from the blast were reported to be recovering in Westminster Hospital.

Thatcher, the club’s only woman member, was attending a European Community summit meeting in Dublin when the bomb exploded at 8:30 p.m. Monday, but she visited the site immediately after returning to London on Tuesday afternoon.

A dozen network television cameras followed her as she poked through the wreckage of the 300-year-old Victorian mansion near Trafalgar Square.

“It is very much worse than I thought,” she declared. “It gets in your throat and nostrils. . . . These people don’t like the results of democracy.”

Thatcher speculated that the bomb may have been timed to coincide with the Dublin summit, asserting that the guerrilla army resented recent progress in Anglo-Irish relations.

The IRA’s statement was issued in Dublin just after Thatcher left, and it confirmed the worst fears of British officials who had predicted that the outlawed group will now target ruling party politicians as well as the British army units that have been similarly attacked in recent weeks.

The IRA wants to drive British forces out of Northern Ireland, and its statement declared, “While such occupation continues, and the nationalist people face daily oppression, the policy-makers and their military arm will not be safe.”

The IRA explained that it targeted the Conservative Party’s posh, 158-year-old private club because it was “the rest and recreation center for the British government, who legislate for a military occupation of the north of Ireland.”

“Like Brighton in 1984, the IRA has brought the war directly to those who keep the British army on the streets and in the fields of Ireland.” The Brighton reference was to the October, 1984, bomb that ripped through the Grand Hotel during the Conservative Party annual conference at the seaside resort on England’s south coast. Five people died in what many consider an assassination attempt aimed at Thatcher.

Monday night’s bomb, which police said was planted between the club’s front door and an inner security door less than an hour before the explosion, was the most brazen attack on the British mainland since the 1984 bombing. And the symbolism was lost on no one.

The bomb, declared London’s prestigious daily, the Financial Times, “had been placed at the heart not only of London, but of the Establishment. Those who placed it had exploded the quiet preserves of members of the British governing class.”

Scotland Yard’s chief of anti-terrorism, Cmdr. George Churchill-Coleman, confirmed at a Tuesday news conference that “there’s not much doubt” that the IRA was behind the attack. “It is clear the same organization is behind the bombings on the mainland. We are dealing with evil and ruthless individuals who have no regard for human life.”

Churchill-Coleman said investigators have determined that the bomb was a sophisticated device consisting of 15 pounds of Semtex plastic explosives. Police are still examining videotapes recorded by a security camera mounted outside the club’s front door for leads to the bombers’ identities, he added.

The attack was timed to coincide with the dinner hour at the club, but, unlike most nights at the club, there were fewer than 20 diners inside at the time, and the most seriously injured was the club’s 76-year-old porter, Charles Henry.

He remained hospitalized Tuesday, as did Lord Kaberry, 82, a member of the House of Lords. Seven others who were injured, including two Americans, were treated at the scene or released after being hospitalized overnight.