A mass brawl outside a McDonald's restaurant in central Perth has left a man with extensive injuries after he was struck with an axe and a meat cleaver.

Four people, including a 15-year-old girl, have been charged with assault. The 46-year-old male victim received numerous cuts and abrasions to his body in the brawl on William Street around 10.20pm (WST) on Wednesday.

A 45-year-old man and a 15-year-old girl, both of Innaloo, have been charged with being armed in public, and assault.

A 40-year-old Innaloo woman and a 23-year-old Wanneroo woman have also been charged with assault.

They will appear in the Perth Magistrates Court and the Perth Children's Court on Friday.

Police are calling for witnesses, and have issued a description of a man they believe can assist them.

He is described as dark skinned, around 175cm tall with slim build and short dark hair.

He was wearing a white zipped-up jacket, with red around the upper chest and neck area and the numbers 05 on the back.

Witnesses are urged to call Crime Stoppers on 1800 333 000.