Northern Territory Police are calling for witnesses in relation to an alleged assault which occurred on public transport yesterday evening.

At about 6:45pm, four unknown men boarded a bus at Casuarina Bus Interchange. A short time later, the 40-year-old male victim boarded the same bus.

At about 7:10pm, the bus stopped on Trower Road between Sabine Road and Francis Street. One of the four men allegedly demanded the victims watch before punching him to the face multiple times.

The four men exited the bus and walked off towards Progress Drive. All four were wearing dark clothing. One man was described as being of Aboriginal appearance, 175cm tall and was wearing a black shirt with large white lettering on the back.

St John Ambulance treated the victim for facial injuries and conveyed him to Royal Darwin Hospital.

Any witnesses are urged to contact police on 131 444 or Crime Stoppers on 1800 333 000. Please quote reference number 9320463.