Four men and a woman are being questioned this morning in connection with the murder of Aidan O'Driscoll in Blackpool on December 7,.
The arrests were made in Blarney and the northside of Cork city this morning.
Three men in their 20s are now being detained under the provisions of Section 50 of the Criminal Justice Act 2007 at Mayfield, Gurranabraher and Bridewell Garda stations.
A man in his 70s and a woman in her 20s are being detained under the provisions of Section 30 of the Offences Against the State Act 1939 at Togher Garda station.
The Ballyvolane man, who was a former Real IRA leader, was on his way to a painting and decorating job in a nearby house when he was gunned down just before 5pm on December 7 on the Old Commons Road.
Investigating officers had originally considered the possibility that the dead man’s past in Limerick and Dublin could have held the key to his killing.
However, investigators now believe the killing was organised in Cork.
A red Opel Astra car believed to have been used to whisk the killers away the Killeens area shortly after the murder was found burnt out just days before Christmas in a ravine in an isolated area between Nadd and Rylane.
Gardaí believe local knowledge was needed by the gang to organise dumping the car there.
It was only spotted by a local landowner but cannot be retrieved from the ravine because it is too deep.
The getaway car used in the murder, a silver Nissan Almera with the registration number 01 TS 1312, was in the general Blackpool area for a number of hours prior to the killing.
That car was found burnt out at Redemption Road.
The gunmen abandoned and set fire to a white Vauxhall Astra van, registered 99 G 12357, in Killeens after the killing, before fleeing in the waiting red Opel Astra.