An 18-year-old man has been arrested after two people were critically injured in an alleged assault near Timaru. 

A police spokesperson said they were first informed of the incident at about 3.20am Sunday morning. 

The spokesperson said two people arrived at hospital with critical injuries, with one then being flown to Christchurch Hospital.

An 18-year-old man is facing a charge of assaulting a person with a weapon. Enquiries are ongoing.