The three dissidents arrested in the two probes are all associates of slain Real IRA leader Alan Ryan, who was shot dead earlier this month.
Security sources said the spy operation at the Garda’s Dublin headquarters was a message that the terror group was “bringing the war” to them.
Two men booked into a front room at the Harcourt Hotel, located directly across from the headquarters at Harcourt Square. They moved in on Tuesday and set up a surveillance operation.
They were taking photo- graphs of the detectives coming and going into the complex and the registration plates of unmarked cars they were driving.
The headquarters house the National Bureau of Criminal Investigation, the Organised Crime Unit, the Special Detective Unit — which combat subversive crime — the Emergency Response Unit, and the Garda Bureau of Fraud Investigation. The Criminal Assets Bureau is also located in the centre.
Garda sources said the men could have used the information to gather details on the homes and families of detectives and used it to intimidate them and detectives generally.
“The Provos have been here before and criminal organisation too,” a Garda source said. “It brings into sharp focus what we are up against. This is a message ‘we are bringing the war to you, you brought it to us’. It’s part of their retaliation and intimidation.”
Gardaí have arrested 20 suspected dissidents recently, and charged three, following paramilitary displays at the funeral of Ryan.
Detectives said the surveillance operation was blown after detectives noticed “suspicious activity” in the Harcourt St area.
They spotted a person “known to them” at the Harcourt Hotel.
They then discovered the person had booked in under a false name and rented a room overlooking the square. When they entered the room they recovered a good-quality digital camera.
Gardaí suspect the men were in the hotel for at least 24 hours.
Officers from the Special Detective Unit arrested the two men on Grafton St.
One man, aged 32 from Tallaght, is a well-known dissident. The second man, aged 41, from Cabra, is also known to gardaí. The 32-year-old was released without charge last night and a file was sent to the DPP. Sources indicated the 41-year-old was also likely to be released.
Meanwhile, gardaí in Meath investigating an assassination attempt on a man who took over the leadership of the Eamon Dunne criminal gang, arrested a 30-year-old known dissident in Tallaght.
Assisted by the Special Detective Unit, they found components of a handgun in the man’s house, which are being examined by ballistic experts. Gardaí are hopeful of bringing charges.