A Christchurch man has a significant head injury, after being smacked the head with a pole when he tried to break up a fight over the weekend.

He was one of three people injured the brawl, where weapons including pot plants, a spade, and a baseball hat were thrown around.

Police investigating the incident have arrested and charged three people.

They're still hoping to speak with a fourth man - estimated to be around 17 years of age, of Maori descent, and of thin build.

Anyone with information is asked to contact Christchurch police.