Two people were assaulted after disturbing an intruder at their home in Christchurch.
Police were called to the incident in Opawa at around 3.30am on Sunday.
An 18-year-old who was returning home disturbed the intruder and they were seriously assaulted.
A family member came to their assistance and was also assaulted, a police spokesperson said.
Police said they believed the intervention of the family member stopped any further assault on the person.
The offender then left the scene, police said.
Both victims required treatment at hospital and are assisting police with enquiries.
Police would like to speak to anyone in the Opawa area who had property disturbed on Saturday evening or Sunday morning or has information that could assist the investigation.
Contact can be made by calling 105 and quoting Police File Number 210613/2503.