The names of all 34 victims of the Dublin and Monaghan bombings have been read out at an event commemorating those killed in 1974.
Wreathes were laid by the Lord Mayor of Dublin, Caroline Conroy and by the Tánaiste Micheál Martin at the memorial on Dublin's Talbot Street.
A minute's silence was held in their memory.
34 people including an unborn baby were killed in a series of "no warning" bombings carried out by loyalist paramilitaries on the evening of 17 May 1974.
This was the greatest loss of life in a single day during the Troubles.
Almost 300 other people were injured in the blasts.
Several relatives of the victims spoke at the event and several expressed concerns at the legacy bill currently making its way through Westminster.
Mr Martin addressed the crowd and told them the Government remained committed to the memory of the innocent victims of the bombings and to finding the truth of what happened.
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"We remember that summer afternoon in 1974: the weekend was fast approaching, and shoppers and workers rushed to finish up for the week, to catch a lift home or meet up with friends," he told those gathered.
"It was Friday, rush hour in Dublin city. As trains arrived and departed a busy Connolly Station, Cleary's clock rang out the hour. With no warning, within minutes, three bombs rang out across the city."
He said that it was "essential that we not lose sight of the atrocities of the past", and said "a shadow had been cast" by the losses and grief of the families searching for truth and justice.
Mr Martin said that days like today were "very very difficult" for the families and anyone affected by the violence of The Troubles, "particularly in terms of unanswered questions".
He said he would continue to press the British government to pause the progress of the legacy bill, which would offer an amnesty to those accused of killings during the Troubles.
"I'm very conscious of this as the British government is coming forward with a legacy bill which we are opposed to, and which all political parties on the island of Ireland are opposed to," he said.
"I think it's very important that in anything governments do, victims have to be centre and the families have to be centre-stage.
"That's why the remembrance today of the worst atrocity during that period is very very important for the families and the generations that come after because on this day 49 years ago the world changed for many many families, for many many communities and its important that we never forget that and that we channel that huge reality of loss into doing the right thing by families of victims."
He said it had raised the issue again with the Secretary of State for Northern Ireland yesterday.
The commemoration event has been organised by Justice for the Forgotten.
Speaking ahead of the memorial, Margaret Urwin of Justice for the Forgotten said the group was "very concerned" about the Bill going through Westminster.
She said that she hoped if the bill becomes law, that the Irish Government would challenge it at European level.
Additional reporting: PA
