Senior IRA commander Brian Keenan has died after a battle with cancer, Sinn Fein said today.
The West Belfast-based republican was a key figure in the organisation during the peace process.
A Sinn Fein spokesman confirmed his death.
Mr Keenan was a former member of the IRA's Army Council who received an 18-year prison sentence in 1980 for conspiring to cause explosions.
The 66-year-old father of six was involved in talks on weapons decommissioning with Canadian General John de Chastelain.
He joined the IRA in 1968 following violence in Belfast and Londonderry and at one stage was described as the single biggest threat to the British army.
In the early 1970s he controlled the arms of the Belfast IRA as quartermaster and was later accused of organising the bombing campaign in England.
He resigned from the Army Council in 2005 due to ill-health.
Sinn Fein president Gerry Adams said the death would come as a shock to all republicans.
"Brian was a formidable republican leader over 40 years of activism," he said.
"He was a man of tremendous energy, even in the face of a debilitating illness."
He added that his dedication to republicanism was unswerving.
"Brian Keenan's strong endorsement of the Sinn Fein peace strategy was crucial in securing the support of the IRA leadership for the series of historic initiatives which sustained the peace process through its most difficult times."
Mr Adams said he was a good friend and steadfast republican.
"He made an incalculable contribution to the republican struggle," he said.
"Brian will be greatly missed by his family and friends and by the many republicans who over the years have been touched by his generosity, friendship, and humour."
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