Two suspects have been arrested over the murder of a man on a halting site during a series of raids by armed gardai.
A woman was also detained after 10 properties were targeted across Dublin and Meath by detectives investigating the murder of Thomas McDonagh.
The 49-year-old father was gunned down at St Margaret's Park, a traveller site where he lived in the Ballymun area of north Dublin, on September 3.
Elite armed gardai, detectives and fraud squad officers took park in the searches in north Dublin, the north inner city, Saggart and Co Meath.
The suspects, aged 37 and 25, were arrested over the murder of Mr McDonagh and can be held for up to a week under Section 50 of the Criminal Justice Act 2007.
The 27-year-old is detained under Section 30, and can be questioned for up to three days.
They are detained at Ballymun and Santry Garda stations.
A Garda spokesman said gardai across Dublin and Meath were backed by armed members of the Eastern Regional Support Unit, Special Detectives Unit, Emergency Response Unit, Garda Bureau of Fraud Investigation and National Bureau of Criminal Investigation.
The Garda Dog Unit, Garda Mounted Unit and Air Support Unit were also involved in the huge operation He said investigators are appealing for anyone with information to come forward.
"In particular, gardai want to hear from any witnesses that observed the culprits getting into a waiting vehicle on the M50 motorway adjacent the Water Tower close to the Finglas exit on September 3 between 9.45pm and 10pm to contact them," he said.