A person has been rushed to hospital in a critical condition after a two-car collision in South Canterbury tonight.

Two cars collided on State Highway One by the Half Chain Rd turn-off at Pareora, south of Timaru, at 7.36pm.

A St John spokesman said one patient's been taken to Timaru Hospital in a critical condition.

Another with moderate injuries has also gone to hospital.

The serious crash unit's investigating.

Diversions are in place via Pareora River Rd while emergency services work to clear the scene.