Four men have been arrested and a haul of nine million cigarettes intercepted by gardai and customs after it was tracked coming through Dublin Port.
The Modeng brand cigarettes were recovered when a truck and a 4x4 were stopped and searched at a service station on the M1 near Castlebellingham, Co Louth.
The black market haul had a street value of about 4.3 million euro and, if sold, would have run up a 3.7 million euro loss to the state.
Gardai pulled the vehicles in at the service station and the arrested me n, three in their late 30s and one in his early 40s, were taken for questioning at Drogheda and Dundalk garda stations.
A number of follow-up searches were carried out in businesses and homes.
The operation involved gardai from the organised crime unit and the Criminal Assets Bureau and customs officers attached to the Revenue.
The cigarettes had been imported into Ireland from Malaysia through Dublin.
The stop and search was described as an intelligence-led operation.
About 35 million black market cigarettes have been seized by the Revenue this year.