An unprovoked attack outside a fast food restaurant in Melbourne‘s north-west left a man needing reconstructive facial surgery, police have revealed.

They are calling for help to find the attacker behind the serious assault outside a Keilor Park fast food restaurant on July 8.

The victim, a 49-year-old Keilor man, was on the patio area outside the restaurant just after midnight when it occurred.

Police are searching for this man after an assault in Keilor Park on July 8. (Victoria Police)

Two men walked past the victim to leave the venue, before one turned back.

Police have said that he then, “without provocation”, struck the victim to the face, causing the victim to become unconscious.

Police do not believe the man knew the victim.

The victim was left with a shattered cheek and needed reconstructive surgery.

Police have released an image and CCTV of a man they want to speak to over the attack.

He is perceived to be Caucasian in appearance and have light brown hair and a beard.

He was wearing a white hooded-top and black pants at the time.

Anyone who witnessed the incident or has information is urged to contact police.