Two dissident republicans are being questioned after surveillance equipment was seized in a hotel room overlooking Dublin's garda headquarters.
Detectives at Harcourt Square in Dublin became aware of suspicious activity near the station when a suspect known to them was observed at the nearby Harcourt Hotel.
A garda spokesman said investigations revealed this person rented a room overlooking Harcourt Square in a false name.
A probe was launched by the Special Detective Unit (SDU) which arrested two men, aged 41 and 32, on Grafton Streett.
"A search of a hotel room near Harcourt Square resulted in the seizure of equipment which it is believed was being used for surveillance purposes," gardai said. "Investigations are ongoing."
Harcourt Square is the Dublin Metropolitan Region Headquarters and houses several specialist units including the SDU which investigates dissident activity, National Bureau of Criminal Investigation, Organised Crime Unit, Emergency Response Unit and Garda Bureau of Fraud Investigation.
The men are being held at Irishtown Garda Station under Section 30 of the Offences against the State Act for membership of an unlawful organisation and providing assistance to an unlawful organisation.
They can be detained for up to 72 hours.