Irish premier Enda Kenny has laid a wreath at the war memorial in Enniskillen, 28 years to the day after the IRA bombed the annual Remembrance Day service.
Eleven people who had gathered to pay respects were killed and dozens more were injured in the no-warning blast in 1987 just minutes before the event was due to start.
A 12th victim of the IRA outrage died 13 years later having never woken from a coma.
Mr Kenny, who leads Ireland’s largest party Fine Gael, became the first taoiseach to attend a Remembrance Day service in Northern Ireland when he took part in commemorations at Enniskillen in 2012.
Every year since he has been invited to return to the Fermanagh town, and every year he has accepted the invitation.
His annual presence at the war memorial is symbolic of the greater recognition now afforded in the Republic of Ireland to those Irishmen who fought and died serving in the British Army in the First World War.
In terrible weather conditions, Mr Kenny joined other dignitaries in laying a wreath at the foot of the memorial.
He placed a laurel tribute before pausing for a moment to bow his head.
Stormont’s Finance minister Arlene Foster and Fermanagh and South Tyrone MP Tom Elliott were among politicians who laid wreaths along with representatives of the Armed Forces and British Legion.
Despite sheeting rain and strong winds, hundreds of people gathered in Enniskillen to watch an annual commemoration that has assumed greater significance and poignancy since the 1987 bomb.
In Belfast, Irish Foreign Affairs Minister Charlie Flanagan laid a laurel wreath at the Cenotaph.
He said: “I am pleased to represent the Irish Government for the second year at the Remembrance Sunday commemoration at Belfast City Hall.
“Men and women from across the island and from all traditions were involved in the First World War, and today’s ceremony is an important opportunity to reflect on their lives and to recognise the impact that this conflict had on countless thousands of families.”
Northern Ireland Secretary Theresa Villiers and First Minister Peter Robinson also attended the event at Belfast City Hall.
More than 200,000 Irish-born soldiers served in the British Army and Navy from 1914 to 1918.
Thousands also joined Britain during the Second World War.