A 70-year-old man has been charged with committing an act of indecency in the presence of people under the age of 16. 

Police say that on early Monday afternoon, three teenagers were fishing on the Molonglo River in Coombs when they noticed a man nearby.

The man then allegedly committed an indecent act, but was disturbed by a passerby who was jogging through the area.

Anyone who was on the Bicentennial National Trail in the vicinity of the Molonglo River and witnessed the incident should call 1800 333000, or via the Crime Stoppers ACT website.