Police believe they may have foiled a major bomb attack today by dissident republicans in Northern Ireland.
A spokesman for the Police Service of Northern Ireland (PSNI) said around 200 to 300 lbs of fully-primed home-made explosives were found when a car was stopped on the outskirts of Armagh city.
He described the operation at "hugely significant".
"But for good police work we would have been talking about deaths and another atrocity in one of our town centres," Assistant Chief Constable Stephen White said later. He added the bomb could have caused an atrocity on the scale of the Omagh bombing in 1998, which killed 29 people.
Northern Ireland Secretary Dr John Reid vowed to stop those behind the bomb from derailing the peace process.
"Those responsible for this simply do not seem to understand that they cannot murder, maul and maim people into their way of thinking," he said.
"Today people are working on a common cause to make Northern Ireland a better place and yet there are still some without a strategy who think they can bomb and blast their way into the past. They have no support, no strategy, no sympathy and they will not succeed."
The driver was arrested and an army bomb disposal team alerted after the discovery of what was suspected to be a bomb in the vehicle. Families in several nearby houses were evacuated.
Army bomb disposal experts later carried out a controlled explosion on the suspect white Vauxhall Astra. The security operation is continuing.
It is understood the man arrested comes from Co Tyrone. His detention followed arrests at the Kilwilkie estate in Lurgan yesterday where a number of weapons, a bomb detonator and ammunition were found. That find was also being linked to dissident republicans.