Koroit police Sergeant Pat Day said the elderly man was walking to his car near the Jamieson Street milk bar just after midday when he saw another male not wearing a mask walking past on the footpath.

"The elderly man said to the other man that he should be wearing a mask and in response has been assaulted," he said.

"The offender, who is described as being in his 40s, of thin build and wearing a blue puffer jacket, has attacked the victim who tried to get into his car.

"The offender has pulled the car door open and punched the victim up to six times to the head

"I have spoken to the elderly victim today who is shaken up, sore but fine."

Sergeant Day said passing tradesmen stopped to help and the offender was last seen running off past VicRoads offices and west into Canterbury Road.

"We are appealing for any witnesses who saw the assault, anyone with dashcam footage or CCTV on their homes or anyone who has information to come forward," he said.

"This is a disgusting act of violence on a vulnerable elderly resident going about his business."

Anyone with information is requested to contact Crime Stoppers on 1800 333 000 or the Koroit police station on 5565 8202.

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