It is understood the victim (50s) and the arrested man are well known to each other.
A post-mortem will take place this morning on the body of a man following a fatal assault in Co. Cavan yesterday.
A man in his 30s arrested on suspicion of murder remains in Garda custody.
Gardaí attended the scene at an apartment in Blacklion in Co Cavan yesterday morning after a man was found unresponsive with serious head injuries.
The victim, a man in his 50s, was later pronounced dead by paramedics.
His body was removed to the mortuary in Navan, Co Meath, where the post-mortem will be carried out.
During follow up investigations yesterday, a man in his 30s was arrested on suspicion of murder.
He’s being questioned at Castlerea Garda Station in Co Roscommon.
It is understood the victim and the arrested man are well known to each other.