Belfast, Northern Ireland (CNN) -- An abandoned van containing a device with 600 pounds of explosives was found in Newry, Northern Ireland, near the border with the Republic of Ireland, police said Saturday.
The device, believed to be linked to dissident IRA groups opposed to the peace process, was "fully primed and ready for use," police said.
The bomb, found late Thursday, was one of the biggest found in Northern Ireland, police said.
It could have caused "death and massive destruction" had it gone off, Chief Superintendent Alasdair Robinson told reporters in Ardmore.
"The device contained two blue barrels with 125kg of homemade explosives in each one, and a detonator -- all the equipment which meant this device was ready to go," he said.
"This was a very significant device -- twice the size of the bomb which was left at Newry Courthouse two years ago. If this had exploded it would have caused devastation.
"To put it in perspective, anyone within 50 meters of this device would have been killed and anyone within 100 meters, seriously injured."
The road leading to the border was closed within minutes after officers became aware of the suspicious vehicle, he said. A member of public raised the alert after driving past the abandoned van, he said.
Robinson said it was too early to speculate on the intended target of the bomb, which was made safe late Friday.
Asked about the threat from dissident groups, he said this was the third attempted attack in the Newry area over the past few weeks, but that all three had been dealt with.
A lawmaker for the area, Northern Ireland government minister Danny Kennedy, said there was no doubt dissident IRA groups were behind the Newry device.
He added: "Clearly this was an attempt to lure police into the area with potentially fatal consequences. My fear is unless these dissidents are dealt with they have huge potential to cause death and destruction."
A small bomb was also found under a parked car in Belfast overnight and disarmed by the army, police said Saturday. Dissident IRA groups are suspected in that attempted attack too although police continue to investigate the motive.
Chief Inspector Ian Campbell said, "Those responsible have shown callous disregard for members of the public and the finger of suspicion points towards dissident republican terrorists."
Police found guns and ammunition in raids Friday targeting IRA dissidents in Belfast.
A rally is being staged in Londonderry later Saturday by mainstream republicans to protest against dissident-linked vigilante groups killing and maiming suspected criminals in the city.