Victoria police are looking for witnesses and warning the public to be careful, after a teen reported being sexually assaulted in a park.

Police say the girl was walking toward Highrock Park Friday evening when a man approached her and started talking about fitness, before suddenly grabbing her and sexually assaulting her.

She got away, they say, but he chased and assaulted her again -- this time exposing himself.

The man is described as tanned or Aboriginal, standing five foot seven with a muscular build, short hair, wearing a t-shirt on his head and a bright red t-shirt with white logo on the front.