Wednesday’s stop on the N2 near Carrickmacross uncovered a completed bomb in a vehicle, and a woman in her 20s and a man in his 40s remain detained.
Garda Commissioner Justin Kelly said the device was not a cache of parts but a ready-to-use explosive with a power unit, detonator and suspected military-grade explosives.
Security sources believe it was probably intended as an under-car bomb for an attack in Northern Ireland, while Irish Defence Forces EOD examined the vehicle after the interception.
The intelligence-led operation targeted dissident republicans, and officials said the device’s sophistication pointed to significant mechanical and electrical skill rather than a crude pipe-bomb threat.
The seizure is likely to sharpen concern over persistent dissident activity and counter-terror resourcing nearly 30 years after the 1998 Good Friday Agreement.