A violent brawl left one man unconscious in Sydney's south on Christmas Eve.

About 11pm on Thursday emergency services were called to the Grand Parade in Brighton-Le-Sands following reports a number of men were involved in a brawl outside an ice cream parlour.

Police were told a group of three men walking along the footpath approached another group of three men who were sitting at tables outside the parlour.

A verbal argument between the two groups erupted into a vicious brawl.