A man is in custody in Castlerea Garda Station on suspicion of murder after an alleged assault in County Cavan.
A man in his 50s died in the attack.
The man was found unresponsive with serious injuries at a home in Blacklion at around a quarter past 9 yesterday morning.
Despite medical intervention he was later pronounced dead by paramedics.
The body of the man in his 50s remained at the scene overnight which has been sealed off for examination by the Garda Technical Bureau.
The office of the State Pathologist has been notified and a post-mortem examination will be arranged for a later date.
A man in his 30s was later arrested on suspicion of murder.
He is still being held at Castlerea Garda Station in Roscommon this morning where he can be detained for up to 24 hours.