Detective Sergeant Chris Asenjo, of the Warrnambool police Crime Investigation Unit, said police believe the man and woman involved were in their 20s and the man punched the woman numerous times in the violent confrontation.

He said the incident unfold in the main street of Mortlake at 5.50pm on Wednesday near a red Ford sedan.

"We're appealing for witnesses. After the incident the victim and offender got into a red Ford sedan and headed towards Warrnambool," he said.

"Someone posted about it on a Facebook buy, swap and sell site and this incident has been the subject of a fair bit of social media commentary."

Detective Asenjo asked people with information about the incident to contact the Mortlake police, Warrnambool CIU or Crime Stoppers on 1800 333 000.