Irish Taoiseach Leo Varadkar has laid a green laurel wreath on Remembrance Sunday in Enniskillen.
In November 1987, an IRA Poppy Day blast in the Co Fermanagh lakeland town killed 12 and injured 68.
Northern Ireland Secretary Julian Smith and DUP leader Arlene Foster also placed floral tributes at the town’s war memorial.
The deputy US counsel general in Belfast left a wreath which quoted former US president Ronald Reagan.
It said: “Their lives remind us that freedom is not bought cheaply.
“It has a cost, it imposes a burden.
“And just as they whom we commemorate were willing to sacrifice, so too must we – in a less final, heroic way – be willing to give of ourselves.”
Veterans from both sides of the Irish border attended.
Crowds packed the narrow street around the memorial.
Wreaths were left by RAF air cadets, the commanding officer of the Royal Dragoon Guards from Catterick Garrison in Yorkshire, a Regimental Association of the Royal Irish Regiment, the local council, Ulster Unionist Party, the Royal Inniskilling Fusiliers Regimental Association and Mrs Foster.
She wrote: “In proud and grateful remembrance of all those who made the supreme sacrifice.”
The IRA bomb detonated during the Remembrance Sunday ceremony in 1987.
Eleven people were killed in the bombing. A 12th, Ronnie Hill, went into a coma and died 13 years later. The Queen and then prime minister Margaret Thatcher sent their sympathies.
The Ballyreagh Silver Band, who played at the 1987 Remembrance Sunday ceremony, provided music for this year’s ceremony.
On Remembrance Day 1997, former Sinn Fein President Gerry Adams apologised for the bombing.
In 2012, Enda Kenny became the first Irish Taoiseach to attend Enniskillen’s Remembrance Sunday ceremony, coinciding with the 25th anniversary of the blast.
It is the second time Mr Varadkar has taken part in the event, and the eighth year that the Irish government has been represented.
The Taoiseach also read a prayer at a service in St Macartin’s Cathedral.