A 26-year-old man has been arrested over the murder of two elderly brothers.
Taoiseach Enda Kenny described the killings of Tommy and Jack Blaine in his home town as an act of savagery.
The pair, aged 68 and 70, who were not married, were discovered in their terraced home in New Antrim Street, Castlebar, Co Mayo, early on Wednesday morning.
The 26-year-old was arrested in the town and taken in for questioning at the local Garda station.
Gardai believe the men died after being violently attacked with blunt force to their upper bodies. A large amount of blood was found at the scene where the bodies were discovered by a home help at about 7am.
Mr Kenny, who has his constituency office on the same street, said he knew the victims very well.
"I was shocked this morning to get a call from my own town where there has been the brutal and savage murder of two men I knew well," he said.
"I find this as an act of savagery. I have spoken to the gardai and I know they are pursuing lines of inquiry and I hope that person or persons responsible are brought to justice in due course."
A Garda source described the two men as vulnerable and said they were last seen at around 10pm on Tuesday night sitting out the front of their house, where they would often be seen greeting locals and passers-by. One of the men was found dead in a bedroom inside the property and the other outside at the back of the house.
Detectives sealed off the house for forensic examination and state pathologist Marie Cassidy carried out preliminary examinations of the bodies and the building to determine how and when the men died.