Belfast - Relatives of the 29 victims of the Omagh bombings in Northern Ireland a decade ago Monday brought civil legal action against five men they believe masterminded the atrocity.

The decision by six families to take their case for compensation before a civil court is believed to be unprecedented in British legal practice, and perhaps even worldwide, legal experts said.

The massive car bombing in the centre of Omagh, a market town in County Tyrone, in August, 1998, in which hundreds were injured, rates as the biggest-single atrocity during the 30 years of unrest in Northern Ireland.

Twenty-nine people and unborn twins died in the attack, carried out by the Real IRA, a hardline off-shoot of the now dissolved underground Irish Republican Army (IRA).

No one has been convicted over the attack after last December a suspect was cleared of involvement at a criminal trial.

But now the families are suing the men they believe were involved in the attack for compensation of more than 10 million pounds (20 million dollars.)

A lawyer representing the families said Monday that it was unprecedented in Britain, and probably anywhere in the world, that "private citizens are confronting terrorists" in the courts.

Those being sued are Michael McKevitt, Seamus Daly, Liam Campbell, Colm Murphy and Seamus McKenna, who all deny involvement in the bombing.

In a further unusual twist, the court will travel to Dublin, the capital of the Republic of Ireland, later in the trial to allow evidence to be taken from investigators there.

Michael Gallagher, who lost his 21-year-old son in the Omagh attack, said Monday that the families took action because they felt let down by the criminal justice system in Northern Ireland and the Irish Republic.

"It's basically left up to victims to seek justice for themselves, but we think it's an important day, regardless of what the outcome of the trial is."

The proceedings are expected to last several weeks. (dpa)