Anti-terrorist detectives seized a massive car bomb in Dublin which was primed and ready to be detonated.
The car with Northern Ireland number plates containing the milk churn bomb was discovered by gardai in the car park of the Finnstown Country House hotel in Lucan, Co Dublin, on Saturday night.
It is understood that dissident republicans are suspected of transporting the device from Belfast to Dublin in recent days.
Sources revealed that it contained 50lbs of explosives made from fertiliser, and was armed and ready for use with a timer attached.
While the intended target remained unclear, the bomb was seized just hours before the culmination of the Giro D'Italia.
The cycling race brought hundreds of thousands of people to the streets of Dublin yesterday.
A source said: "This was a deadly, full-size bomb which had been wired up and ready for imminent use.
"If it had gone off it would have caused total devastation."
It is believed the device was going to be moved from the Lucan car park to its intended target.
Security sources say that the device, made safe by an Irish army bomb squad, would have caused carnage if it had exploded.
It is understood that the device was fitted with a Timer Power Unit (TPU), a hallmark of all major IRA bombs.
Also known as a "safe to arm" switch, the TPU can be set to detonate at a given time, which can range from a few hours to several days or even months after it is set.
A security source said: "It cannot be ruled out that it may have been intended to disrupt the Giro d'Italia race. This would be a very dramatic escalation in the activities of dissident republicans."
It is understood that a Dublin man in his 50s who was later arrested has close links to the Real IRA.
The man is from the inner city and was an associate of murdered RIRA boss Alan Ryan.
Gardai located the device after receiving a tip off and a major security operation was launched.
Hundreds of guests – many of whom had been attending a wedding – were left stranded outside the luxury Finnstown Country House Hotel overnight after the bomb was discovered in the car park.
The alarm was raised at 8.40pm on Saturday in a 999 call to gardai.
Gardai and the Irish army's Explosive Ordinance Disposal unit arrived at the scene a short time afterwards and ordered that the hotel be evacuated at around 10.30pm.
Hotel general manager Gavin Creaton confirmed that there was a "full house" in the hotel at the time.