Northern Territory Police have arrested a 20-year-old male following a sexual assault incident in The Narrows on Friday night.

Shortly before 10pm, police were stopped by a witness who stated he observed a man allegedly sexually assaulting a female. 

Police located the alleged assault in progress before the man tried to leave the scene. Upon speaking with the woman, she stated she was waiting for the bus when the unknown man approached and assaulted her. 

The man was arrested at the scene by police and taken to Darwin Watch House. He has been charged with having sexual intercourse without consent.

The man is due to appear in Darwin Local Court today.