Gardai last night made one of the biggest seizures of dissident republican arms and explosives following a search in Meelick, Co Clare.
The seizure may have averted terrorist attacks in the North and attempts to carry out bombings in Britain.
Technical experts were last night examining the find, which includes a variety of weapons but, most importantly, recently manufactured devices for detonating bombs.
The Garda Special Detective Unit has been searching for a dissident arms and explosives manufacturing operation for more than a year, and the indications last night were that the find in a wooded area in Meelick marked a major breakthrough in that search.
Sources said the haul included several TPUs (timer power units), the key elements in bomb-making, based exactly on the same devices manufactured by the Provisional IRA during its campaign up to the mid-1990s.
Gardai believe that former Provo bomb-makers who had been inactive for years decided last year to join the dissidents and begin manufacturing improvised explosive devices (IEDs) again.
No arrests were made, but it is understood that the seizure was linked to another operation in July in which gardai recovered 15kg of the Czech-made explosive, Semtex, and a variety of weapons and ammunition in Dublin.
Last evening's seizure included a substantial amount of explosives, ammunition, detonators, TPUs, a variety of firearms, CS gas containers, magazines and balaclavas. Full details of the find will be released later today.
Gardai have been investigating links between dissident republicans based in Dublin and Limerick and have had significant successes in the past year since a new group, terming itself the "New Real IRA" and including former leading members of the Provisional IRA, emerged.
The group was able to access weapons and the Semtex explosives which the Provisional IRA claimed to have decommissioned but failed to do so.
Sources said the claims that the Provisional IRA weapons were decommissioned was a fraud and that it was accepted by both the British and Irish governments as an expedient to assist the entry of Sinn Fein into government in the North with the Democratic Unionist Party.
Gardai believe a substantial amount of the Provisional IRA's armoury was hidden from the international decommissioning group which was charged with overseeing the destruction of weapons.
The dissidents in the Republic are mainly based in Dublin and Limerick, with some support in the Midlands. The Limerick dissidents have responsibility for storing and moving weapons.
Gardai have closed in on the network operating south of the Border to supply arms to dissidents in the North who are intent on re-igniting terrorist violence.
They regard last evening's discovery as "hugely important", according to senior sources.
Gardai, PSNI and the British domestic intelligence service, MI5, have had major successes in the past year in thwarting dissident republican attacks, but still regard the threat as "high".
Last March, security forces in the North working in cooperation with gardai seized mortars about to be used against the Strand Road PSNI station in Derry.