A 45-year-old Ukrainian is receiving hospital treatment after allegedly being injured in a fight in St Paul's Bay late on Sunday.
Another man is being questioned about the case.
The police said the victim was found unconscious in Triq Ġulju shortly before midnight and was hospitalised in a serious condition.
A 20-year-old man resident in St Paul's Bay is being questioned.
Magistrate Yana Micallef Stafrace is holding an inquiry.