THE Prime Ministers of Britain and Ireland stood shoulder to shoulder in Belfast last night, vowing to do all in their power to track down the bombers responsible for the worst atrocity in Northern Ireland's 30 years of troubles.

As Omagh struggled to comprehend the enormity of the attack that killed 28 - mostly women and children - and injured 220, Tony Blair and Bertie Ahern reaffirmed their "absolute and unshakeable" determination to achieve peace in the Province.

Mr Blair, who broke off his French holiday to go to Stormont, spoke of his "total shock, horror and outrage at this act of unspeakable evil", while Mr Ahern pledged to crush the self-styled Real IRA, the dissident Republican splinter group being blamed for the bombing. He refused even to rule out the reintroduction of internment.

At the two leaders' request, police chiefs from both sides of the border will hold an emergency meeting this morning to discuss ways of strengthening security and catching the culprits. Mo Mowlam, the Northern Ireland Secretary who flew back from Greece last night, will meet Ireland's Justice Minister.

The victims of Saturday afternoon's blast included at least 14 women and several children, Protestant and Roman Catholic. A woman celebrating her 65th birthday with her pregnant daughter and 20-month-old granddaughter were among the dead. So, too, were a father and son and two visiting Spaniards - a 12-year-old boy and his group leader. One badly mutilated victims has yet to be identified.

Of those who survived, at least 11 remained critically ill in the six hospitals around the Province. Dominic Pinto, the leading surgeon at Omagh's Tyrone County Hospital, said his colleagues were working in "battlefield conditions".

The people of Omagh wept openly at the devastation around them. Relatives waited in quiet desperation as the work of identification continued through the day. Many crowded into churches.

While no group admitted responsibility, Ronnie Flanagan, the Royal Ulster Constabulary Chief Constable, was one of many who identified the self-styled Real IRA as the prime suspect. It is a Republican splinter group based just south of the border and led by a former quartermaster-general of the IRA.

Leading figures from the group's political wing - the 32-County Sovereignty Committee - were lying low. They include Bernadette Sands-McKevitt, the sister of the IRA hunger striker Bobby Sands. Her husband, Michael McKevitt, also has links with the committee but he refused to comment yesterday on either the bombing or any role he may play in Republican splinter groups. McKevitt was named in a Dublin court three months ago as having been arrested in 1988 on suspicion of IRA membership.

The committee issued a statement, however, insisting that it had nothing to do with the bombing, which had left it "deeply saddened and devastated". It added: "The killing of innocent people cannot be justified in any circumstances. We are a political movement and are not a military group."

The Real IRA came under deep suspicion after two telephone warnings bomb using a code that has been used to warn of dissident Republican attacks in the past - the Real IRA used it before the recent bombing at Banbridge.

The police were particularly outraged by the misleading information given in the first warning call. The caller said that a bomb had been left outside the courthouse in Main Street, Omagh. The town has no Main Street, but Market Street is the main shopping thoroughfare.

The courthouse is at the top of Market Street, but the bomb went off 400 yards away at the other end of the street. It was contained in a red Vauxhall Cavalier that had been stolen in Carrickmacross, Co Monaghan, last Thursday.

The bomb played into the hands of Unionists opposed to the peace process. "We were promised peace but we were given war," the Rev Ian Paisley, leader of the Democratic Unionist Party, said. But almost every other political leader, including Sinn Fein's Gerry Adams, insisted that the bombing must not derail the peace process.

For the first time Mr Adams unequivocally condemned an act of violence by fellow Republicans and called for an emergency meeting of all Northern Ireland's political leaders. Mr Adams was one of a succession of leaders to visit Omagh yesterday, including John Prescott and the Irish President Mary McAleese. And in Belfast, Mr Blair visited survivors in the intensive care unit at the Royal Victoria Hospital.

President Clinton, who plans to visit Northern Ireland on September 3, condemned the "butchery", and the Pope denounced the bombers' "blind violence".