The RUC believes weapons found in a car on Sunday night were being transported by dissident republican paramilitaries. One man, believed to be from west Belfast, was arrested following the seizure of arms and ammunition on the M1 motorway at about 9 p.m.
Detonators, ammunition, a sub-machinegun and a sawn-off shotgun were recovered by the RUC. They were discovered in a car which had been travelling in the direction of Belfast when it was stopped at the Sprucefield roundabout outside Lisburn.
Mr Gary McMichael, the Ulster Democratic Party leader, said it was vital that security forces continued to concentrate on eliminating the threat posed by dissident republicans.
"I am concerned that dissidents are moving weapons from the Border areas into the city and fear that they intend to mount attacks on Belfast in the future," said Mr McMichael, whose party has links with the UFF and UDA.
While the items recovered on Sunday are not of themselves very significant, the find is indicative of an increase in dissident republican activity.
The Continuity IRA and the "Real IRA" are thought to have joined forces to smuggle a large consignment of weapons intercepted by police in Croatia last month. This included Russian-made RPG18 rocket-launchers, plastic explosives, detonators and automatic weapons. It is believed the dissidents already have smaller quantities of these.
Dissidents were also blamed for two recent bomb attacks in London. Hammersmith Bridge was damaged in an explosion in June, and on July 20th a device was destroyed in a controlled explosion at Ealing Broadway Tube station. Both attacks were blamed on the "Real IRA".
Since February a number of attacks in the North have also been linked to both the Continuity IRA and the "Real IRA". These attacks have increasingly been aimed at the security forces.
In February a Continuity IRA bomb exploded at a hotel in Co Fermanagh. Later that month a device partially exploded at a British army base in Co Derry and a primed rocket-launcher was found close to another security base in Co Tyrone.
In March three men were arrested after 500lb of home-made explosives were intercepted on their way into Belfast.
There was an explosion at the perimeter fence of an army base in Co Derry in April, and the Continuity IRA was linked to an attempted mortar-bomb attack at a security base in Co Fermanagh the same month. In June a partially-exploded device was found in a field close to the Hillsborough residence of the Northern Secretary.
On July 10th what was believed to be a "Real IRA" carbomb destroyed a house and seriously damaged a petrol station outside Stewartstown, Co Tyrone.