Joggers in Nanaimo, B.C., are being warned to be vigilant after a naked man wearing only a gorilla mask attempted to sexually assault a woman on Saturday.

The jogger was near the one kilometre mark on the popular Westwood Lake trail around 5:45 p.m. when Mounties say the assailant grabbed her by the leg and "rubbed himself against her."

The victim kicked the man and continued running down the trail.

The suspect caught up to her again near the two kilometre mark, possibly by using a shortcut trail. This time the man was wearing shiny black track pants.

"She started to scream and was able to get away, thankfully," Nanaimo RCMP Sgt. Sheryl Armstrong told ctvbc.ca.

The woman caught up with other joggers, who escorted her off of the trail and called 911.

"Exhaustive" attempts to track the suspect using police dogs were unsuccessful. The suspect was spotted earlier in the day masturbating in the bushes.

Police say joggers should always run with a partner and, if possible, carry a whistle and cell phone.

Armstrong said if trail users see someone masturbating, the best thing to do is call police.

"If we can identify him at an early stage then maybe we can get them help," she said.

"It could prevent this from escalating into more deviant behaviour."

The suspect is described as 5-10, 170 pounds with dark hair.