Ian Graham and David Young

The Omagh bombing was "a massacre of the innocents", the opening day of a multimillion-pound civil action against five men believed to be responsible heard yesterday.

Twenty nine people died, including a mother pregnant with twins, and hundreds more were injured when the Real IRA bombed the Co Tyrone town on a busy Saturday afternoon in August 1998.

Some of those who lost loved ones and some who were injured launched the civil action following the failure of the authorities to bring anyone to justice in nearly a decade.

Lord Daniel Brennan, QC, representing them, said the bombing was "one of the most infamous terrorist atrocities in the history of this island".

Opening the landmark action at the High Court in Belfast he said: "It is a civil claim unprecedented - certainly in the UK - and probably around the world.

"For the first time the victims of terrorism are confronting the alleged perpetrators. For the first time private citizens are confronting terrorists in our courts."

The five men accused of carrying out the bombing were not in court. Two are in prison in the Irish Republic and the others chose not to attend.

All have denied involvement and four are represented at the hearing which is expected to last for up to eight weeks - with a week of the hearing in the Supreme Court in Dublin while some two dozen Irish police officers give evidence.

The action, taken by the families affected by the bomb and in the name of Mark Breslin whose wife died in the blast, has been funded by public donations of some £1.2m topped up with £800,000 from the government.

The five defendants from which the families are seeking more than £14m are Michael McKevitt, the alleged leader of the Real IRA, Liam Campbell, said to be his No 2, and Colm Murphy, as well as Seamus McKenna and Seamus Daly.

McKevitt, 58, is currently awaiting judgment in his second appeal against a 20-year conviction in the Irish Republic for directing terrorism.

Campbell, 43, has been held in Portlaoise Prison in the republic on terrorism charges unconnected with Omagh.

Murphy, 56, was sentenced to 14 years in prison in Dublin in 2002 for conspiracy to cause the Omagh explosion, but had the conviction overturned and is awaiting a retrial.

Campbell has not instructed lawyers to defend him and Lord Brennan said that was "deliberate and considered".

The only man to be charged with the Omagh murders is not among those targeted by the families. Last December Sean Hoey, an electrician, walked free from Belfast Crown Court after a judge acquitted him of all charges related to the bombing and a host of other Real IRA attacks.

The courtroom where the case is being heard by Mr Justice Morgan has been especially equipped with state-of-the-art video and computer equipment for the case.

Both side of the ornate wood-lined courtroom have been lined with drab grey metal cabinets stuffed with files of the thousands of documents on which the case will revolve.

Several of the Omagh families sat on the public benches listening intently as Lord Brennan delivered his day- long opening address.

Lord Brennan said the families were seeking aggravated, punitive and exemplary damages against the five men.

If successful, any award would be relentlessly enforced and money would be sought from the men, the Real IRA, the 32-county Sovereignty Movement - its alleged political wing - and the Irish Prisoners Welfare organisation.

Success would send out the message that "every terrorist will have to live in fear that their assets, their homes, their belongings may be taken from them."

The case was adjourned until today.