Christchurch police are investigating a video showing boys kicking and punching a man - and making him eat pet food outside the Riccarton Road McDonald's

The vigilante group believed he was a paedophile, with boys in the video saying "he was trying to meet a 14-year-old girl for sex".

Detective Senior Sergeant Karen Simmons says they're aware of the video, and making enquiries.

At least one student wearing a Christchurch Boys' High uniform can be seen.

Headmaster Nic Hill says the behaviour's unacceptable.

Police say they're working with the school.