Four men, including two from Northern Ireland, have been remanded in custody after a mortar bomb was seized during a sting operation on a suspected Real IRA gang in the Republic.
Army experts worked in freezing temperatures to make safe the improvised grenade launcher.
The bomb disposal operation shut the M1 motorway in Louth near the border for several hours on Tuesday.
Patrick Tierney and Patrick Gordon from Armagh, and Dalton McKevitt and Niall Farrell from Dundalk, Co Louth, appeared at Dublin's Special Criminal Court yesterday.
The rocket launcher was found in a car stopped by gardai as it travelled north on the M1 motorway between junction 16 and junction 17 near Dundalk, at 9.30pm. It was only a few miles from the border when it was intercepted by the elite armed Garda Emergency Response Unit.
Gordon, of Newtownhamilton Road, is accused of unlawfully possessing a mortar launcher with a mortar at a house on Commons Road, Dromiskin, Co Louth, on Tuesday.
When charged, the 22-year-old told gardai: “I am not a member of the IRA and I was only in the car because I was scared.”
Dublin's three-judge non-jury Special Criminal Court heard Tierney (25), of Drumarg Park, was charged with possessing a mortar launcher with a mortar at Dromiskin. He made no reply after caution.
McKevitt, of Woodbury Gardens, was charged at Balbriggan Garda Station, north Dublin. He is understood to be a distant relative of convicted Real IRA leader Michael McKevitt.
The 35-year-old said nothing when charged with membership of the Real IRA and the unlawful possession of an improvised mortar launcher with a mortar at Dromiskin.
Farrell, of Clos Brid, was charged at Santry Garda Station and made no reply.
The 34-year-old is accused of being a member of the Real IRA and unlawfully possessing a mortar launcher at the same location.
All four men were remanded in custody to appear before the court again on Wednesday, when bail applications are expected to be made.