FRESH doubts hang over the loyalist ceasefire after gardai confirmed the bomb near Sinn Fein's Monaghan offices contained 26lb of a type of commercial explosive used in the past by the UVF.
The bomb, believed to have been planted by the UVF on Sunday night, failed to explode, although its detonator went off early on Monday.
The attack prompted a warning last night from the Irish Republican Socialist Party (IRSP) of the danger that its military wing, the Irish National Liberation Army (INLA), could strike back.
The Monaghan bomb contained 25 sticks of a commercial explosive manufactured under the trade name Powergel 900, which is used mostly in the mining business. The UVF had used this type of explosive in attacks on both sides of the Border before its ceasefire.
If the bomb had exploded, it would have wrecked the back of several premises in Dublin Street, Monaghan, including the office of the local Sinn Fein representative, Mr Caoimhghin O Caolain.
Sources close to the loyalists said Mr O Caolain was targeted because of his relatively high profile in the party in the Republic.
Mr Billy Hutchinson, leader of the Progressive Unionist Party (PUP), which has links with the UVF, said all the evidence pointed to the fact that the UVF was responsible for the bomb. If so, it would have "very big implications" for his party, he said.
Mr Hutchinson said loyalists were under serious pressure but people shouldn't "jump up and down" if it was a breach of the ceasefire and demand that loyalists be excluded from the talks process.
He said: "Our understanding was that we had convinced people the way forward was through political dialogue and accommodation rather than through bombs and guns. We'll have to go back now to the drawing board ... If it was the UVF and it has been sanctioned at the very highest level and it isn't some renegade, then we have some serious work to do on the ground."
Mr Hutchinson said if the UVF was responsible for the bomb, it must claim it and let the people of Northern Ireland know it is "going back to war".
"It was unfair to put the people of Northern Ireland through this without telling them that it was going to happen," he added.
Mr Hutchinson said he hoped the bomb was "some sort of measured response or isolated incident rather than a sign that they (the UVF) are prepared to return to war".
He said his party was working to "convince the people in the UVF and Red Hand Commandos that the way to secure the union is through political dialogue and accommodation ... What I have to do is to investigate this, find out what it is about and then try to resolve it - and that's our job. The whole of the PUP will be doing that over the next couple of days."
Mr John White from the Ulster Democratic Party (UDP), which has links with the UDA, said his understanding was that the loyalist ceasefire was intact and he had heard nothing to contradict that.
The president of Sinn Fein, Mr Gerry Adams, urged republicans to be "extremely vigilant". He said he was aware of "increased loyalist targeting" of republicans in the North with "known members of loyalist death squads" identified in nationalist areas in recent weeks.