A teenager has been charged with sexually assaulting a four-year-old Aboriginal boy in a remote Western Australian town.

The alleged assault, described by investigators as "disturbing", occurred last Thursday afternoon in bushland near the Kimberley town of Halls Creek.

A member of the public reported the incident to police who charged the Indigenous teenager on Friday with two counts of sexual penetration of a child under 13.

Detective Sergeant Tania McKenzie from Kununurra Police said the alleged incident was one of a number of child abuse investigations currently underway in the town.

"Kununurra Detectives have recently done some different jobs in Halls Creek in relation to child abuse," she said.

"We're very thankful to the people that bought it to our attention and that we were able to make an arrest very quickly."

She said the alleged behaviour was particularly shocking for the small community.



Det. Sergeant McKenzie praised the community for raising the alarm and implored local families to prioritise the safety of their children.

"Please just be aware where your children are and be aware of their surroundings," she said.

The ABC understands neither child is currently under the care of the Department of Communities, Child Protection and Family Support.

Child Protection Minister Simone McGurk and Member for Kimberley Josie Farrer have been contacted for comment.

The teenager remains in custody and is expected to appear in Perth Children's Court on Friday.

Department of Communities spokesperson Jackie Trang said staff are working with WA Police to ensure the safety of all concerned.

"As this matter is before the court, it would be inappropriate for the Department to many further comment," she said.

The Department of Communities' Halls Creek Unit manages 37 children in care.