Politicians on all sides paid tribute on Tuesday to Martin McGuinness, Northern Ireland's former deputy first minister and an ex-commander of the Irish Republican Army, who died overnight aged 66.
"It is with deep regret and sadness that we have learnt of the death of our friend and comrade Martin McGuinness who passed away in Derry during the night. He will be sorely missed by all who knew him," Irish republican party Sinn Fein said in a statement.
McGuinness, a pivotal and controversial figure in the British-administered province for three-and-a-half decades, was in 2007 installed as deputy first minister in a power-sharing executive between rival Protestants and Catholics.
He resigned from that post in January.
"Throughout his life Martin showed great determination, dignity and humility and it was no different during his short illness," Sinn Fein president Gerry Adams said.
Arlene Foster, who served alongside McGuinness as Northern Ireland's first minister until January, said news of his death would "come as a shock to many people."
"First and foremost, Martin McGuinness was a much loved husband, father and grandfather," said Foster, who leads the rival Democratic Unionist Party (DUP).
"My thoughts and prayers are with his wife and the family circle at this very painful time of grief and loss," she said.
Kyle Paisley, the son of DUP founder Ian Paisley, remembered "the remarkable year he and my father spent in office together and the great good they did together."
"Will never forget his ongoing care for my father in his ill health," Paisley said on Twitter.
Colum Eastwood, leader of the moderate Social Democratic and Labour Party (SDLP), said McGuinness's "remarkable journey from paramilitarism to peace was a hallmark of the transformative effect of the peace process."
"The loss of Martin McGuinness is a significant moment in the history of this island," Eastwood said.
"It is appropriate that we reflect on Martin's remarkable journey, made possible by men and women from all traditions across this island who forged a peace process from the fire of a terrible conflict."
Peter Hain, a former Northern Ireland secretary for the British government, said McGuinness had been "such a pivotal, essential figure in the Northern Ireland peace process."
"While not forgetting the past, no one can doubt the essential role he played in helping to secure the power-sharing arrangements and political progress in Northern Ireland," said James Brokenshire, the current Northern Ireland secretary.
Born in the predominantly Catholic city of Derry in 1950, McGuinness was widely regarded as being a central figure on the Army Council of the IRA.
McGuinness had admitted to being a member of the terrorist organization during the 1970s as violence broke out following the failure of the Irish nationalist-led civil rights movement.