Two men remain in custody on Saturday following their arrest in connection with the murder of dissident republican Vincent Ryan last month.
A 43 year-old man was arrested on Thursday evening and is being held at Blanchardstown Garda station.
This arrest followed the detention of two men aged in their 30s following Garda searches in a number of buildings in north and west Dublin on Tuesday.
One of these men has since been released. The other remains in custody at Finglas Garda station.
Mr Ryan (25), the brother of murdered Real IRA chief Alan Ryan, died in hospital after he was ambushed and shot a number of times as he sat in a car outside his partner’s home in Dublin.
Mr Ryan was sitting in a white Volkswagen Golf at about 3.15pm after dropping his partner and infant child to their home on McKee Road in Finglas.
Another car pulled up alongside and an occupant fired a number of shots into Mr Ryan’s car, hitting him in the head and body.
The attackers’ car sped from the scene and was later found burnt out in Co Kildare.
Mr Ryan had been warned his life was in danger, and this was the second time in a few months he had been targeted.