A woman who was waiting for a bus in The Narrows Friday night was allegedly raped by a 20-year-old man in a horrific incident that NT Police did not publicly report until Monday afternoon.

NT Police media manager Rob Cross said in a statement that police were stopped by a witness on Friday night shortly before 10pm who told them he had seen a man “allegedly sexually assaulting a female”.

“Police located the alleged assault in progress before the man tried to leave the scene,” Mr Cross said.

“Upon speaking with the woman, she stated she was waiting for the bus when the unknown man approached and assaulted her.”

Mr Cross added that the man was arrested at the scene and taken to the Darwin Watch House where he was later charged with sexual intercourse without consent.

He was due to appear in court today.

Police did not provide an update on the condition of the woman.

The NT Police media unit has come under intense criticism for months over repeated failures to report sexual assaults to the public in a timely manner.