Belfast priest, Fr Alec Reid, described as one of the architects of the peace process, has died.
He acted as an intermediary between the IRA and politicians.
According to the BBC, Fr Reid died in a Dublin hospital early today.
Sinn Féin's Martin McGuinness has paid tribute, saying he is very sad to learn of his death.
He described him as "An extraordinary and humble Priest who made an immense contribution to Peace."
Very sad to learn of the death of our dear friend Fr. Alex Reid. An extraordinary & humble Priest who made an immense contribution to Peace.— Martin McGuinness (@M_McGuinness_SF) November 22, 2013
Sinn Féin president Gerry Adams said Fr Reid's base in west Belfast during the Troubles, Clonard, was "the cradle of the peace process''.
“I feel deeply saddened. I have not absorbed it yet. I knew him for the last 40 years,” he said.
“He was also a very good friend of mine, of my wife, of my family.
“What Alec Reid did was he lived the gospel message. He developed a view which was contrary to the official view, that there had to be dialogue, and he was tenacious – I remember quite a few times saying he was like a terrier.”
Mr Adams told RTE Radio he was with Fr Reid last night in St Vincent’s Hospital, Dublin, and had been due to visit him again today at midday.
Mr Adams described Fr Reid as ``a chaplain to the peace process''.
He said: “This was one person making a difference when in the entire establishment had refused to open up dialogue.
“And the whole credo of his gospel life was the dignity of human beings and the need for dialogue.”
The Sinn Féin president paid tribute to the priest for initiating talks with former SDLP leader John Hume, and noted his friendship with late Taoiseach Charlie Haughey.
He also referred to Fr Reid’s work with the Basque peace process.
Mr Hume described the late cleric, who hailed originally from Co Tipperary, as a "pillar of the peace process''.
“Without his courage, determination and utter selflessness, the road to peace in our region would have been much longer and much more difficult to traverse,” he said.
“A man of faith and deep conviction, his commitment to our people was a key part of the foundation on which our early, fragile peace was built.
“Fr Alec was not simply a ’go-between’ in the early days of negotiating for peace. He was an active player in fighting for an end to violence.
“Few will forget the image of Fr Reid lying between Corporals David Howes and Derek Wood in an attempt to save their lives in March 1988. His dedication was to all people, regardless of their background.
“While we mourn the loss of a great man, we must also celebrate the legacy of peace and an opportunity to reconcile our people that he gave to us. It is an opportunity we cannot afford to waste.
“I wish to send my deepest condolences to his family, friends, his fellow priests and brothers of the Redemptorist Order and all those whose lives he touched.”
Tánaiste and Minister for Foreign Affairs Eamonn Gilmore said he made a huge contribution to the peace we now enjoy on this island.
Alex Attwood, Stormont MLA for west Belfast, said: “He lived out his faith conviction in the lives of people. This place and our people are the better for all of his work.”
The cleric had a long association with Clonard Monastery on the Falls Road in Belfast, from where he forged a close relationship with Mr Adams.
A key confidant of Mr Adams, he acted as a vital communications link between the Sinn Féin leader, then-SDLP leader John Hume and the British and Irish Governments in the late 1980s and 1990s as early peace process dialogue developed in secret.
Years later, with paramilitary ceasefires delivered and the 1998 Good Friday peace accord signed, he was one of two churchmen who acted as independent witnesses to the decommissioning of the IRA’s arsenal of weapons in 2005.
The presence of the cleric and Methodist minister the Rev. Harold Good were vital in convincing those sceptical of the republicans’ pledge to put their guns beyond use.
The priest once famously recalled that an armed IRA member present for the decommissioning act handed over his assault rifle, which Fr Reid said became the last weapon to be “put beyond use”.
“The man handed it over and got quite emotional,” said Fr Reid. ”He was aware that this was the last gun.”
Northern Ireland Secretary Theresa Villiers paid tribute to the cleric.
“I heard with sadness of the death of Father Reid,” she said.
“We all owe a debt of gratitude to him for the role he played in the peace and reconciliation process in Northern Ireland.”
Current SDLP leader Dr Alasdair McDonnell said: “I was very saddened to hear of the passing of Father Alec Reid who dedicated his life to ensuring peace was realised on this Island.
“His death reminds us that we haven’t quite reached completion in terms of the peace process and we must re-double our efforts to achieve a lasting settlement.
“The courage and bravery displayed by Father Reid during the troubles has been a shining example to people right across the world.”