Gardai have seized 18 firearms and approximately 900 rounds of ammunition at a premises in Co Louth.
At approximately 2pm, officers carried out a search on the outskirts of Ardee.
They seized six AR-15 assault rifles and 12 semi-automatic 9mm handguns.
Approximately 900 rounds of 9mm and .223 ammunition were also discovered.
A number of follow-up searches were carried out at several properties in the county.
Two men in their 30s were arrested on suspicion of participation in the activities of a criminal organisation to facilitate firearms trafficking.
Assistant Commissioner for Organised and Serious Crime Justin Kelly said: “Today’s seizure of firearms and ammunition is particularly significant.
“These would have undoubtedly been used to maim, kill and intimidate those in communities across Ireland.
“Weapons such as those seized by Gardai today are the lifeblood of organised criminal groups – who often use violence as part of their drug trafficking operations.
“I wish to commend the dedication of all the Gardai involved in this operation.
“Operations like today’s demonstrate our determination to make Ireland a hostile environment for organised criminal groups to operate.”