Tensions between local Greek and Macedonian communities are believed to be behind the violent attack of a man at a family-friendly restaurant in Melbourne's north-east last week.

Police are investigating after a number of men set upon a man in his 20s at a Ribs & Burgers restaurant on McDonalds Road in South Morang on December 17.

Three men, who were at the restaurant with a larger group, assaulted the victim about 7.40pm, before fleeing the scene and leaving him with minor facial injuries and small fracture on one finger.

The Age has been told the group was punching the victim, who is of Greek heritage, in the head and face for up to 40 seconds. The victim's car was also damaged.

The attackers have not been arrested by police and the investigation is ongoing. Detectives have secured CCTV footage from the restaurant.