Two men have been charged following an alleged aggravated sexual assault of a teenage girl in Goulburn on Wednesday.

Police have been told the young teenage girl was at Wollondilly River when she was allegedly approached by three males sometime between 4pm and 5pm.

It is alleged the girl was then sexually and indecently assaulted.

The girl, whose age has not been released, alerted her mother who contacted police.

Two Goulburn men, aged 18 and 38, and a Goulburn teenager were arrested a short time later in a Victoria Street home.

They were taken to Goulburn Police Station, where the two men were charged with aggravated sexual assault with a person under the age of 16. They were later refused bail and were due to appear in Goulburn Local Court on Thursday January 16.

A third male under the age of 18 was released pending further inquiries.

Multiples witnesses may have seen the alleged incident, Goulburn Local Area Command Acting Superintendent Evan Quarmby said.

“On hot days, the river area is an area frequented by swimmers and people walking dogs,” Acting Superintendent Quarmby said.

“We are appealing to any person who may have been in the area and seen anything at the time to contact Goulburn Detectives or crime stoppers on 1800 333 000."

Anyone with information can also use the Crime Stoppers online reporting page.