A suspected mortar tube and a “substantial quantity of ammunition” have been recovered by police close to the Irish border in County Louth.
Gardaí (Irish police) and the Irish army are taking part in the searches on lands near the village of Omeath on the Cooley peninsula.
In a statement, the Gardaí said the operation is “targeting the activities of dissident republican groups”.
The searches began on Friday morning. No arrests have been made as yet.
The operation is being led by Garda Special Detective and Emergency Response Units.
Irish army explosives experts are also involved and a safety cordon is in place.
Searches are expected to continue into Saturday.
The suspected mortar tube will be examined by Garda ballistics experts.
Irish national broadcaster RTÉ reported that the haul is being described as “significant”.