Tommy Crossan, the Continuity IRA's former commander in Belfast, a prominent dissident republican, has been gunned down in Northern Ireland.
Crossan was shot dead in the grounds of an industrial complex in West Belfast, in full view of surrounding houses, a local representative said.
A priest attended to pray over the bloodied victim in an area long known as a republican heartland but which has been relatively peaceful in recent years following the end of the IRA campaign in 1998.
Nationalist SDLP councillor Colin Keenan said: "We have long hoped that the shadow of death had been lifted from West Belfast.
"Today's event is a terrible, tragic reminder of the violent conflict of the past."
Crossan was reportedly the Continuity IRA's former leader and was believed to be the subject of a death threat from his former allies.
The organisation has opposed the peace process which largely ended three decades of violence and transformed the region.
The attack happened at the Peter Pan Centre in Springfield Road, the Police Service of Northern Ireland (PSNI) said.
The road, one of the main arterial routes, has been closed to traffic.
Family members have arrived and are said to be devastated.
A PSNI spokesman said: "Police are investigating a fatal shooting in the Springfield Road area of West Belfast this afternoon.
"One man has been shot dead in the vicinity of the Peter Pan Centre."
The largely-nationalist area of Belfast is mainly made up of tightly-packed terraced housing estates and businesses.
Mr Keenan said it was a horrific scene.
The CIRA murdered Police Constable Stephen Carroll in Lurgan in Co Armagh in March 2009. It has since been riven with splits.
Members of the security forces have been on high alert for attacks by various extremist factions who have also killed two soldiers and a prison officer.
In recent weeks they have stepped up efforts to kill police officers, with several attacks on the force in West Belfast.
After the murder of prison officer David Black on the M1 motorway in November 2012, police mounted an unprecedented surveillance operation against various factions as well making significant arrests.