A Christchurch police officer will need surgery for a broken nose, after stepping in to help a teenage girl who was being assaulted.
The attack occured at a party at about 10.30om on Friday, at a house in Riccarton Road.
A police spokesperson says the sergeant saw the girl being assaulted by a man and stepped into help.
But the girl began to punch and kick the officer in the head, and was joined by others.
A 17-year-old male faces charges including assaulting a female, and will appear in the Christchurch District Court on Tuesday.
A 14-year-old girl has been charged with assault with intent to injure and will appear in the Youth Court next week.