Wreaths have been laid at the site of one of three bombs which exploded 40 years ago in the single worst day of atrocities in the Troubles.
Relatives of the dead and survivors of the 1974 Dublin-Monaghan bombings gathered at a memorial on Talbot Street in the Irish capital.
Taoiseach Enda Kenny laid a wreath along with the members of the Justice for the Forgotten group, which announced last week it is suing the British Government to get access to classified files they believe will confirm collusion.
Thirty-three people were killed, including a pregnant woman, and almost 300 people injured in the no-warning UVF bombs, three in Dublin and one in Monaghan, in the space of 90 minutes.
Irish Foreign Affairs Minister Eamon Gilmore increased pressure on Prime Minister David Cameron to release information on the bombing on the back of the announcement of the lawsuit.
Justice for the Forgotten's Margaret Urwin said: "We hope it will be followed up by action by the British."
Northern Ireland Secretary of State Teresa Villiers said she would continue to hold talks with the Irish Government over the bombings.