York Regional Police released a sketch of a man accused of striking a teenage victim with a gun before sexually assaulting her in Aurora earlier this week.

Police say the assault happened just before noon on Monday while the victim was walking in the trails west of John West Way north of Wellington Street.

According to police, she was approached by the suspect who was allegedly armed with a handgun.

The victim was taken to hospital and treated for minor physical injuries.

The suspect is described as being in his 20s with a light-brown skin tone, and thin build.

He was wearing a black shirt, black pants and a red baseball cap.

Police want to connect with a man who was jogging in the area at the time who they say the girl sought help from following the assault.

Police are urging anyone with information to contact the York Regional Special Victims Unit or Crime Stoppers to leave an anonymous tip.