The RUC has said it believes dissident republicans are responsible for the 500lb cache of explosives found by police near Hillsborough, Co Down, on Wednesday night. Three people arrested in connection with the find were still being questioned by detectives last night.
The officer in charge of the investigation, Chief Insp Ken Henning, yesterday refused to be drawn on whether he believed the "Real IRA", the organisation responsible for the Omagh bomb in August 1998, was linked to the cache..
Police made the find when they stopped two cars on the main A1 dual carriageway, eight miles from Belfast. Security forces believe the explosives were being driven to Belfast to be made into a bomb, to be used possibly during St Patrick's Day celebrations, or in an attack on the security forces.
The seizure comes after a number of attacks by dissident republicans in recent months. In early February, a bomb extensively damaged a hotel in Irvinestown, Co Fermanagh. Another bomb partially exploded just outside the sleeping quarters in a British army base in Ballykelly, Co Derry. A primed rocket launcher was discovered close to another army base, in Dungannon, Co Tyrone.
Chief Insp Henning said he condemned "without hesitation" the transportation of the home-made explosives on a public road.
"To transport that amount of explosives in a vehicle on a public road is highly dangerous. We condemn it outright. Five hundred pounds is a considerable device and would have caused considerable damage."
The Northern Secretary, Mr Peter Mandelson, speaking from Washington where he is attending St Patrick's Day celebrations, praised the RUC for preventing a "possibly appalling outrage".
"I warmly commend the RUC for their highly professional police action in stopping what could have been an appalling outrage. It shows the need to maintain effective security levels."
Unionist politicians echoed the Northern Secretary's sentiments, saying it was vital to maintain a sufficient security force presence to counter the threat posed by paramilitaries.
The Ulster Unionist security spokesman, Mr Ken Maginnis, said the seizure vindicated his party's position of insisting on a complete decommissioning of all paramilitary weaponry.
The Ulster Unionist MP for Lagan Valley, Mr Jeffrey Donaldson, said the bomb's interception had averted possible destruction and loss of life.
"The discovery of this bomb again highlights the absolute necessity for the decommissioning of illegal terrorist weaponry and explosives. Those who would propose that unionists shift from their present position on decommissioning are not living in the real world."
Mr Donaldson added that the Dublin Government's demand for a reduction in security was "totally irresponsible" and would leave the people of Northern Ireland "vulnerable and exposed".
Meanwhile, the republican weekly, An Phoblacht, has claimed that a bomb consisting of British military explosives was defused on west Belfast's Falls Road by an IRA volunteer several weeks ago.
The RUC said officers had searched the area extensively on two occasions and had not found anything.