Northern Territory Police are investigating an alleged sexual assault in Rapid Creek this morning.

Police received a report of a female being allegedly assaulted at approximately 5:30am. The female was threatened with a knife before another person intervened and the offender fled the scene.

Detectives from the Sex Crimes Section are continuing with enquiries.

Anyone who witnessed the incident or has any information is urged to notify police on 131444 or Crime Stoppers on 1800 333 000.