A man found lying on the ground in an uncommunicative state wearing a blood-stained shirt in Birżebbuga last night is critical, the police siad.
The man was found in Triq San Patrizju, at 8pm yesterday.
They said the man was taken to Mater Dei Hospital by ambulance.
The police said they are investigating claims that the victim, whose identity is not yet known, fell and hit his head against a wall.
An inquiry is being held.