Thousands gathered in the Northern Ireland town of Omagh on Friday to mark the 10th anniversary of the worst single atrocity during the three-decade conflict in the British province, the dpa reported.
A car bomb in the County Tyrone town on August 15, 1998, killed 29 people, including a woman pregnant with twins. The attack was carried out by the Real IRA, a dissident Irish Republican group.
A minute's silence was held in heavy rain to mark the moment the bomb went off.
The memorial service was attended by relatives, community representatives and politicians including Irish Prime Minister Brian Cowen and Northern Ireland Deputy First Minister Martin McGuinness.
A glass monument at the bomb site and a new memorial garden nearby were unveiled.
However, a support group of victims' relatives boycotted the ceremony because of a controversy over the wording of an inscription on the memorial.
Irish national broadcaster RTE reported the Omagh support group were unhappy with the omission of any mention of the group responsible for the killings on the new memorial structure.
Irish President Mary McAleese said in advance of the ceremony that "Omagh '98 will always be remembered for the horrific loss of innocent life and the terrible suffering caused to so many. But the way that its people responded to that tragedy will also mark Omagh '98 as a monument to the triumph of hope over despair."
Cowen said that "as we continue to build a peaceful and a better future, [the Omagh bombing] remains an indelible stain on our history that will never be forgotten.
"Our thoughts and prayers are with those who were killed and injured, and all of those who still grieve for their loss and who continue to search for justice."
A Mass to remember the victims in Dublin's Catholic Cathedral on Friday morning was attended by around 800 people, RTE reported.
No-one has ever been convicted in relation to the attack. Northern Ireland's police chief Hugh Orde has said it is unlikely anyone ever would be convicted unless new evidence comes to light.
Relatives of the victims are taking a civil case against named individuals they hold responsible for the atrocity.