Dissident republicans who prepared a 500lb van bomb risked causing an Omagh-style massacre, politicians in Northern Ireland have said.
Detectives believe the bomb, found at an underpass near the border on the main Belfast to Dublin road, may have been destined for a town centre attack.
Twenty nine people were killed and 220 were injured in a republican bomb attack in the centre of Omagh, Co Tyrone, in August 1998.
While it is believed the presence of a police checkpoint forced the latest bombers to abandon the vehicle, hundreds of motorists drove past the deadly device unaware of the danger after traffic cones and warning signs had been removed, and even driven over, by others on the road.
The blue Ford transit van, stolen in Maynooth outside Dublin in January and carrying false Donegal registration plates, was found near Newry and contained a wheelie bin packed with 500lbs of homemade explosives.
The foiled attack is being blamed on dissident republicans opposed to the peace process, who last Saturday killed constable Ronan Kerr in a booby-trap bomb in Omagh. The device that killed the officer detonated not long after a fun run had passed the scene.
Politicians have condemned the latest bomb bid, which they said could have caused a massacre on the scale of the Omagh attack when the dead included a woman pregnant with twins.
Policing Board member Jonathan Bell compared the failed attack to the infamous bombing of the Co Tyrone town.
The DUP representative added: "500lbs of explosives were planted to kill and we could have had another example of mass murder on our hands today.
"Just as last week we had many children and families running past the explosive device that robbed our society of the life of a talented young officer, so today we could have had serious fatalities. As our police raise their activities commensurate with the threat they face, so we must give them our full support."