Northern Territory Police are calling for witnesses following an assault of a 40-year-old male in Darwin CBD overnight.

At around 8:30pm, police received information that a male had been assaulted on Lindsay Street.

The man suffered serious head injuries and was taken to Royal Darwin Hospital for treatment.

Police are urging anyone with information to contact 131 444 or CrimeStoppers on 1800 333 000. Please quote reference number 9330306.