Nine men are being questioned by detectives investigating dissident republican activity.
The suspects were arrested during a series of raids across Limerick city and county on Monday morning.
No firearms were recovered during the planned operation.
The men, aged from their 30s to 50s, can be held for up to a week under Section 30 of the Offences Against the State Act.
Four are being held at Henry Street Garda Station, with two in Roxboro Road, and one each in Mayorstone, Newcastle West and Askeaton.