Gardaí seized about €700,000 worth of various drugs during two planned raids on Wednesday.
In Finglas, north Dublin, heroin, cocaine and herbal cannabis were found with an estimated value of €580,000.
A firearm and ammunition were also recovered during the operation at a premises in the Barry area of Finglas shortly after 4pm.
A man, in his late 30s, was arrested at the scene and is being held at Finglas garda station.
Meanwhile, in Limerick, gardaí seized €126,000 worth of various drugs during an operation targeting organised crime.
Herbal cannabis, cocaine, benzodiazepines and alprazolam were all discovered at a property in Brooksbridge, Pallasgreen, Co Limerick on Wednesday afternoon.
The search, which was carried out as part of Operation Thor, also uncovered two firearms, ammunition and a gun component. No arrests were made.