Lives were saved by the discovery of a suspected major dissident republican bomb-making operation in the Irish Republic, Justice Minister Dermot Ahern said yesterday.
Two men were arrested and component parts of a potentially significant explosive device were seized in last night's planned raid by gardai in Dundalk, Co Louth.
Among the items discovered at the outbuilding on the Old Newry Road in the town's Mount Pleasant area were two large modified gas cylinders fixed on to a trailer.
It is believed the swoop could have foiled an imminent attack in Northern Ireland similar to those carried out in recent months by extremists opposed to the peace process.
Mr Ahern said the threat from dissident groups remained strong but insisted authorities north and south of the border were determined to tackle them at every turn.
"Last night's operation was very successful. Lives have been saved as a result," the minister said.
"The harsh reality is from time to time relatively small groups of people can succeed in committing violent acts.
"But these people will have to get the message one way or the other that their activities are doomed to fail."
The suspects, aged 23 and 52, were taken to Drogheda Garda station for questioning. They can be held for up to three days under Section 30 of the Offences Against the State Act.
Meanwhile the arrest scene, in an area surrounded by houses and factory units, remained sealed off as experts from the Garda Technical Bureau conducted forensic examinations.
Gardai and PSNI detectives have been working closely to thwart the dissidents, with intelligence suggesting many bomb operations have been planned and prepared in the Republic.
Mr Ahern - who last month met with Northern Ireland's new Justice Minister David Ford, Garda Commissioner Fachtna Murphy, and PSNI Chief Constable Matt Baggott - said north-south co-operation on security matters had never been better.
Later this week the minister and new Secretary of State for Northern Ireland, Owen Paterson, will publish the latest Independent Monitoring Commission report on the dissident threat.
"It will not surprise anyone," Mr Ahern said.
"The threat from dissident groups is severe."
But he warned dissidents they had little support within their communities.
"I have no doubt that their campaign, which is based on the proposition that they can kill and bomb their way to a United Ireland, will ultimately fail utterly.
"Dissidents are throwbacks to a dreadful time on this island which the vast majority of people have democratically put behind them."