Seven people are being questioned over a gangland-style murder in a rural village.
Shane Rossiter became the 14th victim of gun crime this year when he was shot dead in a house just yards from a church in Golden, Co Tipperary, on October 17.
Gardai said five men and two women - aged from their early 20s to early 40s - have been arrested in the Tipperary area.
"They are currently detained in various Garda stations in the Co Tipperary area," they added.
They can be held for up to three days under Section 30 of the Offences Against the State Act 1939.
Rossiter, 30, who had drug and burglary convictions, was shot in a house and rushed to South Tipperary General Hospital in Clonmel, where he was pronounced dead.
His teenage brother Brian died 10 years ago after he fell into a coma in Garda custody in their hometown of Clonmel.
His family, including parents Pat and Siobhan, had campaigned tirelessly for an inquiry, which later ruled there was no evidence of an assault on the 14-year-old, who had been arrested for an alleged public order offence.
A probe into his death, set up in September 2005, found that while his arrest was lawful, his detention was unlawful.
While it stated there was no evidence to suggest an assault in custody, it hit out at the force for not properly investigating all the circumstances surrounding the death and criticised officers for failing to observe certain custody procedures.