A 53-year-old man has been arrested by Gardai investigating dissident republican activity.
A firearm and a quantity of ammunition were also discovered when officers stopped and searched a car on the Dundalk to Ardee Road last night.
Another weapon and stolen car were also recovered during a follow-up search at a premises in Co Louth.
The suspect is being held at Dundalk Garda station under the Offences Against the State Act.
A spokesman for An Garda Siochana said the arrest was part on an ongoing investigation.
Officers from the Special Detective Unit were assisted by members of the Emergency Response Unit during the operation.