Two men were arrested and €550,000 worth of suspected cannabis and cocaine were seized following six searches in Monaghan and Galway on Thursday.
A Rolex watch, four cars and €65,000 in cash were also seized by gardaí following the searches.
The searches involved detective and drug unit personnel in the Louth/Cavan/Monaghan and Galway divisions.
A garda statement described the seizure as a major operation targeting an organised crime gang suspected of involvement in the importation and sale of controlled drugs in the north-east and west of Ireland.
The arrested men are in their 40s and 50s and are currently detained at a Garda station in accordance with the provisions of Section 2 of the Criminal Justice (Drug Trafficking) Act, 1996.
The seized drugs will now be forwarded to Forensic Science Ireland for further analysis.
Investigations are ongoing.
