Police are continuing to investigate Friday's discovery of a cache of ammunition in the Omeath area on the Cooley Peninsula near the border with Northern Ireland.
"During the searches to date Gardai [Irish police] have recovered a substantial quantity of ammunition of varied calibre along with a mortar tube [pending examination by Garda ballistics experts]. A Garda operation is currently underway in County Louth [in eastern Ireland] as part of ongoing investigations targeting the activities of dissident Republican groups," police said on Friday.
The statement came a few days after a group calling itself the New Irish Republican Army (IRA) claimed responsibility for detonating a car bomb in the city of Londonderry in Northern Ireland on 19 January.
While no one was injured or killed in the bombing, authorities in Northern Ireland and the European Union warned that the incident raised terror threats across the region and spiked fears over the dangers of a hard border between the Republic of Ireland and Northern Ireland.
The new IRA, in turn, denied that Brexit motivated it to plant the bomb, adding that the group's fight "goes on".
"We also caution those who collaborate with the British that they are to desist immediately as no more warnings will be given," the group said.
British Prime Minister Theresa May has repeatedly reiterated London's push to stop the formation of a hard border between Northern Ireland and the Republic of Ireland after Brexit.
The issue has proven to be an obstacle in Brexit talks, as London's exit from the EU might create difficulties in terms of free movement of goods and workers between the Republic of Ireland and Northern Ireland. Britain's scheduled exit date from the bloc is for March 29, 2019.