The Garda are questioning seven men as part of their ongoing investigation into the activities of dissident republican groups.
The men were arrested last night after a search of a house in Dundalk where ammunition and arms were discovered.
The men, aged between 20 and 50, are being questioned under Section 30 of the Offences Against the State Act. They can be held without being charged for up to 72 hours.
A search of the house is continuing.