04/03/2013 10:52 GMT | Updated 04/03/2013 14:06 GMT

Dissident Irish Republican Bomb Plot In Londonderry Foiled, Four Mortars Seized (VIDEO, PICTURES)

Police in Northern Ireland have condemned 'reckless' dissident republicans over a foiled bomb plot that could have caused mass casualties.

Four primed mortars were seized minutes before the terrorists planned to blitz a police station in Londonderry after officers rammed a van carrying the bombs which were just about to be launched through a hole cut in the roof.

Police forensic officers examine the car in which four mortar rounds were found in Londonderry

Two men were arrested, one of whom had been following behind on a motorbike. A third was detained later. All were known to the Derry police.

More than 100 homes had to be evacuated and families moved out while army explosives experts examined the mortars.

The devices had been recently constructed and were similar in design to the type of bombs manufactured and used with such devastating effect by the Provisional IRA before they called a halt to their terrorist campaign in July 2005.

Nine officers were killed when a police station in Newry, Co Down, was hit in a missile attack in February 1985.

Senior officers in Derry believe the van was on its way to be parked near a police station and the devices then triggered from a specially constructed launch pad in the back of the vehicle.

Chief Superintendent Stephen Cargin said there could have been massive carnage if the van had not been intercepted.

He said: "I have no doubt they could have caused mass casualties. We could have been looking at mass murder today if they had hit their intended target."

Two of the detained men are aged 37 and the third is 35. One of them was driving the van when officers swooped in a major undercover operation in Lone Moor Road.

Just 48 hours earlier, more than 5,500 men, women and children had gathered on the opposite side of the River Foyle to smash the record for the biggest song-and-dance routine by performing a number from the hit musical Annie.

Republicans suspected of supporting or being involved in acts of violence are under constant police surveillance in Derry amid fears the dissidents are intent on disrupting the UK City of Culture programme.

It seemed apparent that security chiefs had good intelligence in advance of this latest security operation.

Martin McGuinness described the plot as 'a vanity trip' and 'more about money and ego than patriotism'

Northern Ireland secretary Teresa Villiers said: "It is a grim reminder of how severe the terrorist threat remains in Northern Ireland."

Politicians on all sides, including Martin McGuinness, the Northern Ireland deputy first minister and a former IRA commander in Derry, condemned the dissidents.

He said it was quite clear the PSNI had managed to foil many of the recent attempts by a small number of people to bring death and destruction onto the streets, and that it was through good work they were not talking about a disastrous situation in Derry.

Mr McGuinness said: "If the people involved in these actions believe that they can by attempting to carry out armed actions undermine the political process, then they are greatly mistaken.

"Whatever differences may exist between the parties in Stormont we are all absolutely united in our efforts to stand up against violent attempts to undermine the political progress already made, be they from loyalist flag protesters or those involved in incidents like last night.

"There is no going back to the past. The community in Derry City and elsewhere simply will not allow it.

"The groups still wedded to pointless armed actions need to reflect on that political reality, because if they continue on their current path all that will be achieved is more people in prison.

"This is not about any attempt to advance a united Ireland. This is a vanity trip by those involved, and more about money and ego than patriotism."

SDLP MP for Foyle Mark Durkan said: "These mortar bombs are not precision devices - and God only knows where any one of those four devices could have gone or the damage it could have done.

"We have all been spared an awful catastrophe - not only in physical terms to buildings or our infrastructure, but also in human terms."

East Londonderry MP Gregory Campbell claimed: "We were 10 minutes away from a disaster. That is how close we were to a really bad night in Londonderry.

"The mortars were ready to be fired. There could have been dozens of people killed."

Irish Taoiseach Enda Kenny said the minority of people who want to draw Ireland back to the Troubles will not achieve their ambition.

"I'm glad that these dissidents were apprehended and that these mortars taken out of commission," Mr Kenny said, attending a British-Irish Parliamentary Assembly in Letterkenny, Co Donegal.

"I want to assure everybody that as far as the government is concerned, the government will work very closely with the Assembly and the British government, and that relations between the PSNI and gardai remain at the very highest level."

Northern Ireland's first minister Peter Robinson praised the police for thwarting the terror attack.

Speaking after a meeting with PSNI Chief Constable Matt Baggott at Stormont on Monday evening, Mr Robinson said: "I congratulate the police on the timely intervention in Londonderry, which could have caused massive loss of life and injury had it been, in the terms of the terrorists, successful.

"It is important to recognise that the basis of that is good, intelligence-based policing and it is important that we continue to have the co-operation of the local community to be able to stop acts of that kind taking place."