Lawyers representing the families have lodged a legal document which confirms the scale of the damages they want awarded against Michael McKevitt, 51; Liam Campbell, 38; Colm Murphy, 51; Seamus McKenna, 49, and 33-year-old Seamus Daly.

Twenty-nine men, women and children died and hundreds were injured when the Real IRA detonated a car bomb in the County Tyrone town on 15 August 1998 - a Saturday when the centre was full of shoppers.

Lawyers for the relatives said the three-inch thick "statement of claim" detailed the agony they had endured.

We have cleared another hurdle and are now in the final stages now before we get to court Michael Gallagher

Michael Gallagher, whose 21-year-old son Aidan died in the explosion, said the High Court action was not about money.

"Hopefully this will send a clear message that terrorism is not a profitable business to be involved in," he said.

"We have cleared another hurdle and are in the final stages now before we get to court."

He said the civil action was expected to be heard in Belfast later this year.

Writs were served against all five last July by the relatives' solicitors.

'Face of indifference'

Jason McCue, who represents the families, said the compensation action was the relatives' final hope.

"This marks yet another historic step in the families' four-year campaign to bring the atrocity before the court," he said.

"This civil action remains their best and last chance for justice.

"They have pursued this claim through enormous grief, with self-sacrifice and determination and, at times, in the face of indifference."

Two of the men who were served with civil writs accusing them of carrying out the Omagh bombing are to contest the case brought against them.

Michael McKevitt and Liam Campbell are being detained at Portlaoise prison in the Irish Republic

Solicitors acting for Liam Campbell and Michael McKevitt lodged papers with the High Court in Belfast declaring their intention to defend themselves last August.

Both men are being held in Portlaoise Prison in the Irish Republic on terrorist offences unconnected with Omagh.

They accepted the writs when a lawyer went to their cells, but Murphy, who is also being held there, refused.

Last year, Colm Murphy received a 14-year jail sentence for plotting to cause an explosion at the time of the Omagh bomb.

He is the only person convicted in connection with the bombing.