Seamus Mallon, one of the architects of the Good Friday Agreement, has died at the age of 83.
Mr Mallon served as deputy First Minister of Northern Ireland from 1998 to 2001.
He also spent 22 years as deputy leader of the SDLP, and was involved in the civil rights movement in the 1960s.
The County Armagh native was a staunch opponent of the use of violence throughout the troubles.
Seamus Mallon was an Irish Patriot. He lived for our country and has left an indelible mark on the lives of everyone who enjoys the peace he helped forge.
I'm proud to have called him a friend. My prayers are with Orla, Mark and Lara. https://t.co/aU9mJRJwB6 pic.twitter.com/QO7Dy3Fi9S
— Colum Eastwood (@columeastwood) January 24, 2020
President Michael D Higgins was among those who paid tribute to Mr Mallon.
He said: "His reputation as a politician and community activist of unsurpassed courage, civility and fairness is held by all those who had the privilege of knowing him.
"Few people have influenced the peace process in Northern Ireland more than Seamus Mallon, a formidable opponent and, a tough negotiator in speech and act, but always honest and honourable."
SDLP leader Colum Eastwood described Mr Mallon as a "force of nature".
He added: “In the darkest days of conflict, when hope was in short supply, Seamus represented the fierce thirst for justice that ran through the SDLP and through communities that had lost so much to political violence."