CCTV captures unprovoked attack against Melbourne man

Police are hunting a man who bashed a Frankston mechanic unconscious in front of the victim's girlfriend as the couple walked home from the movies, resulting in the loss of his sense of smell and taste.

The victim, who wishes to only be identified as Jason, told 9NEWS he was attempting to ignore the taunts from a man following him and his girlfriend.

"They were mouthing off to us, asking to fight me, saying he wanted to fight," he said.

"It's just unfair, I didn't do anything to deserve it."

However the man caught up to them and began raining blows on the 19-year-old, unable to defend himself.

Caught on camera, the video shows the assault was also witnessed by the attacker's friend, who stands by and does nothing.

The attacker beats Jason relentlessly, body-slamming him into the ground, leaving him limp and unconscious.

"Absolutely no connection between the two parties, and completely unprovoked," Constable Ben Vandenberg said.

"It's pretty callous and cowardly and we really want to catch this offender ... we don't want him doing it to another person."

Jason's girlfriend was unable to wake him up and ran to get help. He lay motionless for several minutes until paramedics took him to hospital.

Jason said he has not been out since the night of the bashing, and has lost his senses of smell and taste as a result.

The attacker and his friend fled down Wells Street, CCTV following their movements as they turned right into Keys Street.

Crime Stoppers is urging three women wearing Mexican hats seen speaking to the men at Frankston Railway Station to come forward.

The offender is Caucasian in appearance, 173cm tall and aged in his early 20s.

Anyone who recognises the man is urged to contact Crime Stoppers on 1800 333 000.