Northern Ireland has charged a man with 29 counts of murder in the 1998 Omagh bombing, the worst attack in decades of violence in the province, police said.
Just months after a peace deal was struck, 29 people, including a woman pregnant with twins, were killed and more than 200 were wounded in the attack. No one has been criminally convicted for it.
Seamus Daly, who lives in Culloville, County Monaghan in the Republic of Ireland, was arrested on Monday when he crossed the border into Northern Ireland, Reuters news agency reported.
The "Good Friday" peace agreement largely ended more than three decades of violence in which more than 3,600 people died between mainly Catholic Irish nationalists, seeking union with Ireland, and predominantly Protestant unionists who want to remain part of the United Kingdom.
The peace has remained largely unbroken, though the province suffers regular tensions between the communities and small groups of dissidents opposed to the agreement still commit sporadic acts of violence.
The only man to stand trial on a murder charge for the Omagh attack was acquitted in 2007. The Real IRA, an IRA splinter group opposed to the peace accord, claimed responsibility.
Daly is one of four men who was found to have been responsible for the bombing in a civil action taken by some of the families of the victims in the absence of a successful criminal conviction.
The four were ordered by the Northern Ireland High Court to pay 1.5 million British pounds ($2.5 million) compensation. No money has ever been paid and Daly has consistently denied being involved.
Daly also faces two charges in relation to a car bombing in Lisburn in April 1998, a police spokesman said. He will appear in court on Friday to have the charges formally put to him.