A mortar-type device has been discovered in north, police said.
Troops involved in a major security operation close to the Border in south Armagh in recent days discovered the device.
Soldiers used sniffer dogs and metal detectors to scour hedgerows and culverts near the village of Cullyhanna.
A PSNI spokesman said: “Police can confirm that the suspicious object found in the Bog Road/Lisleitrim Road area of Cullyhanna is a mortar-type device. Army technical officers are continuing to examine and make safe the device.”
Republican dissidents opposed to the peace process are suspected to be behind the discovery.
Ulster Unionist MLA Danny Kennedy described the discovery as distressing.
He said he was concerned “at both the capability and the intent” of those behind the find “and it simply reinforces how important it is that local people give total support to the police and provide them with every assistance possible as they attempt to protect and serve the entire community”.
“I would appeal for anyone with any information to come forward immediately and help the police to catch whoever was responsible for this incident.”
In March, a mortar attack on a police station in Derry was foiled after the security services stopped a van with four viable devices primed and ready to launch.
Two men were arrested and were remanded in custody after appearing before a judge in the city.
Mortars have also been found during security alerts in Belfast.