Security and republican sources have confirmed that the Provisional IRA was responsible for the murder of Charles Bennett, who was buried yesterday.
IRA sources claim he was killed to pacify hardliners anxious over decommissioning and the lack of political progress.
Mr Bennett (22) was found shot in the head on waste ground in west Belfast last Friday. He was blindfolded and his hands had been bound. Mr Gerry Adams yesterday described the killing as "a terrible tragedy" for his family.
"There has been a lot of speculation surrounding Charles Bennett's death. His family deserve to know the truth," he said.
Although neither the RUC nor the British government has officially blamed the Provisional IRA, security sources have insisted that no other group was involved.
Yesterday, the Junior Minister for Foreign Affairs, Ms Liz O'Donnell, sidestepped the security assessment when it was put to her.
"Any assessment of whether a ceasefire has been breached is one based on security intelligence, obviously, but also on fine political judgment from the ministers involved and the two governments," she said after a meeting with Mr George Howarth, the newly appointed political development minister in Northern Ireland.
Ms O'Donnell was responding to a question on her understanding of the IRA ceasefire in the light of reports that the security forces in the North believed the IRA was responsible for the murder of Mr Bennett in Belfast.
Republican sources privately admitted Mr Bennett had been killed because the Provisionals - to whom he was believed to have links - were experiencing serious internal problems even in Belfast, traditionally a leadership stronghold. One source compared the situation to a previous spate of killings of drug dealers by the Provisionals using the "Direct Action Against Drugs" name.
"They were aimed at pacifying certain discontented elements in the ranks and this is the same," he said. "It reassures those elements that the war is not over and the IRA has not gone away."
He was not suggesting that Mr Bennett had any connection with drugs, the source insisted.
The UK Unionist leader, Mr Robert McCartney, last night demanded that the Northern Secretary, Dr Mo Mowlam, state if she believed the murder of Mr Bennett was a breach of the IRA ceasefire. Two men have been arrested in connection with the killing. Their names have not been released.
The British Prime Minister's chief of staff, Mr Jonathan Powell, is to have talks today with Orange Order leaders to try to end the standoff at Drumcree.
A separate meeting between Mr Blair's adviser and the Garvaghy Road Residents Coalition has been called off, according to a spokesman for the Northern Ireland Office last night. The spokesman said it was hoped those discussions could take place later.
The residents have objected to the Orangemen marching on the nationalist Garvaghy Road.