A 20-year-old Dundalk man has appeared before the Special Criminal Court in Dublin charged with unlawful possession of ammunition and an explosive device.
Gerard Carroll of Ashling Park, was one of five men arrested on Friday night when police stopped cars on a motorway close to the border in County Louth.
The court heard that at the time Mr Carroll was in possession of a 24-volt modified battery-operated hand tool.
In a follow-up search of his home eight rounds of ammunition were found.
He made no reply when charged.
No application for bail was made and he was remanded in custody to appear again next week.
Three other men arrested during the same operation have been released and a file is being prepared for the Director of Public Prosecution.
The fourth man is still in custody.