Four men have been arrested in connection with the murder of Aidan Byrne in February.
Three of the men are in their 20s, while the fourth man is in his 30s.
The four were arrested in Dublin this morning.
They are being detained at the Bridewell, Pearse Street, Store Street and Mountjoy Garda stations.
Mr Byrne, 33, was shot dead as he sat in the passenger seat of a car at Drumalee Avenue off the North Circular Road.
