Gardaí have detained a woman at an address in Blackhall Place in Dublin and uncovered bomb-making components as part of an ongoing Garda operation against dissident republican paramilitaries.
The latest arrest was made hours after three men had been held in a car stopped by gardaí near Dundalk in Co Louth.
In that move, too, gardaí discovered equipment for manufacturing bombs, including explosives. While arresting the woman, who is in her 30s, gardaí found timing power units.
The woman was tonight being questioned in a Mountjoy garda station.
Two of the men detained in Co Louth, both from Dublin, were also being questioned at a garda base in Dundalk. The third man, from Dundalk, was being questioned by detectives in Ashbourne, Co Meath.
All four are being held under the Offences Against the State Act. They can be held for up to 72 hours.