Update at 8.15pm:
Gardai investigating an assault in Monaghan have arrested a 19-year-old male this evening in the Monaghan area. He is currently being detained at Monaghan Garda Station.
Update at 5.30pm:
A man in his 20s is in a critical condition in hospital after an assault in Monaghan.
He was found on the side of a roadway just before midnight last night when gardaí were called out to a disturbance at Woodview in Killygowan.
The man had serious head injuries and was taken by ambulance to Cavan General Hospital and later removed to Beaumont Hospital in Dublin.
Gardaí are appealing for any witnesses to come forward.
A technical and forensic examination of the scene has been carried out.