Gardai are investigating two seperate alleged assaults in Dublin City Centre last night.
A man has been arrested after a serious assault on another man at South Great Georges Street.
At approximately 2.45am while on patrol, gardaí came the assistance of a man, who is in his 20s, with serious head injuries.
He was taken to St James Hospital for treatment. His injuries are not thought to be life-threatening.
A man aged in his late teens was arrested in connection with the incident a short time later and is currently detained at Pearse Street Garda Station.
The scene remains sealed off this morning.
Gardaí are appealing for witnesses following the alleged assault incident to contact Pearse Street Garda Station 01 6669000 or The Garda Confidential Line 1800 666 111.
Meanwhile, another man in his 20s was brought to hospital with minor facial injuries after an alleged assault on Townsend Street, which happened at around 10.50pm last night.
Gardaí arrested four men, all in their 20s, in connection to this incident.
All four have since been released without charge, and a file is being prepared for the DPP.