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.

29 New Jobs To Be Created As Chemist Warehouse To Open In Naas Tomorrow
Date Set For Jozef Puska's Appeal Against His Conviction For The Murder Of Ashling Murphy
Vulnerable Adults, Some Using Wheelchairs, Forced To Share Inaccessible Vehicles At Kildare HSE Service
“Grabbed By the Neck”: Founder Tells Kildare Today Why She Launched New Female-Focused Taxi Service
Just 75% Of Landowners On Board So Far As Uisce Eireann Submits Plans For Major Water Supply Project
Two Kildare Animal Charities Share €170k Fund As Animal Welfare Costs Continue To Mount
Call To Make Extended Christmas Train Timetable Permanent For Commuter Towns
Roadside Memorial Ban Proposal Criticised Over Christmas Timing