Searches have been conducted in Limerick, Dublin and Cork as part of the investigation into the murder of Shane Geoghegan.
The searches were also part of a wider operation against gang-related crime.
One house in east Cork searched by gardaí had been used by a man with close ties to the McCarthy-Dundon gang.
It is understood that the man no longer lives at that address.
A number of items, including phones and documents, were seized during the raid at the house in Cobh.
Gardaí say they are searching for firearms and other evidence that may be useful in the fight against those involved in criminal activity.
It is understood members of the ERU and the National Surveillance Unit backed up by the garda helicopter are involved in the searches.
Dáil debate
Minister for Justice Dermot Ahern says the Government will rule nothing out which is consistent with the rule of law in tackling armed criminal gangs.
Mr Ahern was speaking during has told a Dáil debate on the killing of Shane Geoghegan. Watch the Dáil debate live.
The 28-year-old fitter and rugby team captain was murdered in Limerick over the weekend when gunmen apparently mistook him for a man associated with one of the feuding gangs in the city.
TDs from all sides of the House conveyed their sympathies to Shane Geoghegan's family.
Mr Ahern said the murder had invoked horror and revulsion and said no resources would be spared in tracking down those involved.
He said the forthcoming covert surveillance legislation will enable gardaí to enter and place bugging devices on private property.
The minister also dismissed the possibility of using the testimony of a chief superintendent as evidence in gang-related cases.
Fine Gael Justice Spokesman Charles Flanagan said the justice system was severely dysfunctional.
He said Mr Geoghegan's murder must be the catalyst to bring about change.
