Security sources have claimed the "Real IRA" was responsible for a planned mortar bomb attack which may have been aimed for Remembrance Sunday in Co Fermanagh. However, republican sources have said it is too early to state authoritatively which dissident organisation was responsible.
Four men were arrested after the "barracks buster" device was found by the RUC close to the Border on Saturday night. They were still being questioned at Gough Barracks in Armagh last night. Sinn Fein has refused to condemn the bomb attempt.
Local party Assembly member Mr Gerry McHugh said an attempted mortar bomb attack would "not help anyone" and would undermine the position of those "trying to move forward to a peaceful future for everyone".
However, he added: "The idea of condemnation doesn't actually help at this time. If you want to help the situation, you will show that politics is working."
Republican sources have said grassroots pressure recently forced the Sinn Fein leadership to reverse its previous policy of condemning dissident republican activity.
The party also failed to condemn a Continuity IRA bomb attack in Castlewellan, Co Down, in which two RUC officers were injured earlier this month. Sinn Fein began condemning dissident attacks following the 1998 Omagh bombing.
However, the condemnations proved unpopular with republican grassroots. Sources said there was a particularly hostile reaction to Mr Martin McGuinness's condemnation of the bombing of a security base in Stewartstown, Co Tyrone, in July.
The mortar bomb discovered last weekend contained 250lb of explosive. It was found in the back of a van stopped by police near the village of Derrylin, Co Fermanagh. Two-way radios and false number plates were discovered in three abandoned cars.
Before the arrests, an RUC officer fired two warning shots in the air.
The Continuity IRA has previously been the most active republican paramilitary group in Co Fermanagh.
However, security sources yesterday said they believed the "Real IRA" was responsible. There is also speculation of renewed co-operation between the two dissident organisations.
Relations between the groups at leadership level have sometimes been fractious but they are said to have improved since the killing of "Real IRA" member, Joe O'Connor, in west Belfast last month. At grassroots level, there has often been co-operation between the two organisations.
The Northern Secretary, Mr Peter Mandelson, said he hoped all the North's political parties would "speak up and condemn" the perpetrators who were "people who want to sabotage what we have achieved". The UUP Environment Minister, Mr Sam Foster, congratulated the RUC on discovering the bomb but added that it was "sad that so much evil still lurks out there in the undergrowth".