A Blast Rips N. Ireland's Grasp on Peace

The prime ministers of Britain and the Irish Republic suddenly are battling to save the peace agreement in Northern Ireland.

Britain's Tony Blair and Ireland's Bertie Ahern have been catapulted into action after a 500-pound car bomb, which police say was planted by renegade republican terrorists, killed at least 28 people and injured 220 Saturday in the market town of Omagh, some 60 miles west of Belfast.

The attack was the most severe challenge to the peace pact since it was signed April 10. And it represented the worst terrorist atrocity in the last 30 years of violence in Northern Ireland.

Mr. Blair, calling the bombing a "blast of evil," interrupted his vacation in France to fly to Belfast. Mr. Ahern called an emergency meeting of top advisers. The British and Irish governments agreed to work together to head off further terrorist attacks.

President Clinton condemned the "butchery" and said his upcoming visit to Northern Ireland would go on as planned.

The two governments' efforts will be focused on two key fronts:

* Finding and detaining members of three small breakaway republican groups thought to be working together to shatter the peace agreement that was backed by a 70 percent majority of Northern Ireland voters in a referendum. British security sources say the groups are based in the Irish Republic but operate across the border in Northern Ireland.

* Persuading signatories to the agreement to remain calm and refrain from political recrimination or acts of retaliatory violence.

Protestant leader David Trimble, the first minister of Northern Ireland's new assembly, returned from vacation in Germany and said there could be no excuse or reason for such a "murderous terrorist onslaught."

Blair will be under pressure from Mr. Trimble and other Northern Ireland Protestant politicians to postpone the planned release from prison of convicted terrorists under the terms of the peace agreement.

In Dublin, Mr. Ahern called his security advisers together to consider drastic action against dissident republicans, who continue to use violence to try to cut ties to Britain and join with the Irish Republic. Internment (arrest without charges or trial) of known extremists was among the most radical steps being considered by the Irish government.

The dissidents are believed by police to be based in the Irish Republic and to have traveled to Northern Ireland to plant the Omagh bomb.

GERRY ADAMS, president of Sinn Fein, the political wing of the Irish Republican Army (IRA), issued a brief statement saying, "I am totally horrified by this action. I condemn it without any equivocation whatsoever." It was the most forthright condemnation of a terrorist act Mr. Adams had ever issued.

Adams is bound to come under increasing pressure to exercise influence over renegade republican groups and to begin the handover of weapons and explosives called for in the April accord. "If ever there was a golden moment for Gerry Adams to disassociate himself from fundamentalist republicanism, this is it," Paul Bew, a professor of Irish politics at Queen's University, Belfast, told the BBC yesterday.

Three small groups, all made up of former members of the IRA, are known to be cooperating to wreck the agreement. They are:

* The Irish National Liberation Army (about 40 members).

* The Continuity IRA (about 30 members).

* The "real" IRA (about 90 members). The "real" IRA was formed last October by IRA terrorists who rejected the leadership of Adams, who they claimed had betrayed the republican cause.

Members of the three groups held a "rejectionist summit" in Dundalk, in the Irish Republic, in June. British security sources say the groups agreed to join forces. Two weeks ago a bomb, thought to be their work, was planted in Banbridge, County Down.

Police in Belfast say the "real" IRA's members include the IRA's ex-quartermaster, a bombmaking expert with access to secret caches of explosives, including the type of detonator police say must have been used in Saturday's attack.

The bombers employed an unusually ruthless method. In the past, republican terrorists often issued advance coded warnings of bomb attacks so that bystanders had a chance to move away ahead of the explosions.

But Northern Ireland police chief Ronnie Flanagan said yesterday that those who planted the device in the middle of a crowded shopping center in Omagh, a town with a mixed Catholic and Protestant population, appeared to have deliberately misled police about its location.

A telephone call had indicated that it was near a courthouse. When police led crowds away from the courthouse, the bomb exploded in the supposedly safe area to which the shoppers had been moved.

Some of the shoppers had been attending a celebration of the April agreement in the city center. The death toll includes both Protestants and Catholics and at least five children, one just 18 months old. Hospitals list many more as critically injured.

Blair's decision to return to Britain reflected fears, shared by Ireland's Ahern, that the peace agreement is in peril and that Northern Ireland may have been pushed to the brink of a new round of tit-for-tat reprisals between Catholics and Protestants.

The Rev. Ian Paisley, leader of the hard-line loyalist (Protestant) Democratic Unionist Party, said, "Nothing happens in Northern Ireland without the IRA knowing about it. At the very least, they turned a blind eye."

Professor Bew adds that the actions of dissident republicans are designed to provoke loyalist retaliation and "thus unleash the sectarianism the peace agreement was designed to curb."