Gardai have been carrying out searches at the murder scene

Jim McAllister said the family of Paul Quinn, from Cullyhanna, believed the IRA had abducted and murdered him.

Mr Quinn, 21, was found at farm buildings at Tullycoora near Oram in County Monaghan on Saturday.

On Monday, Sinn Fein leader Gerry Adams said republicans were not involved in the murder.

The DUP has said conclusive IRA involvement "could mean the collapse of the political institutions".

However, Mr Adams said: "Others may want to play politics with this dreadful murder. I don't and I won't."

"There is no republican involvement whatsoever in this man's murder and all of us should be careful that we don't end up playing politics with what is a dreadful, criminal action."

Mr Quinn was found at farm buildings near the village of Oram

He said whoever was responsible for the killing should be brought to justice.

Mr McAllister, a member of the 1982 NI Assembly, said the murdered man had received two threats from republicans.

Mr McAllister said the killing had been "a brutal slaughter" by a gang wielding iron bars.

He said two men who worked on the farm had been tied up and forced to phone Mr Quinn to lure him to the area.

'Serious implications'

"He went to the farm with a friend... they separated Paul Quinn from the other three," said Mr McAllister.

He said he did not want to speak on radio about the reports he had heard about the beating Mr Quinn had received in the barn.

The victim had been involved in fights with the son of a leading republican and an associate of high-ranking republicans, he said.

Mr Quinn was beaten by up to 15 men in a barn

DUP MP Jeffrey Donaldson said if it was found that the IRA were involved in the murder it would have serious implications.

"If the IRA were corporately involved in this murder, that may mean that the executive is finished in its current form.

"But we do not yet know and we have to wait until we get all of the facts - but it could mean the collapse of the political institutions.

"That has happened before - it may happen again."