An angry mob smashed the windows of a man's car and then attacked him with weapons in Christchurch.

The incident, involving eight to 10 people, happened at the new Riccarton Rd bus depot about 6.50pm on Thursday.

Detective Senior Sergeant Leairne Dow said it appeared a group of people had walked down Division St and smashed the windows of a man's car.

They then entered the depot and attacked the man with weapons, which police were still trying to identify, Dow said.

A St John spokesman said the victim was taken to Christchurch Hospital with minor injuries to the back of his head.

Dow said police were reviewing CCTV footage of the incident.​ The motive was unclear, she said.

Anyone with information should call police on (03) 3637400 or Crimestoppers anonymously on 0800 555 111.