Motorists are being warned to expect delays following a serious crash in Christchurch.

Emergency services were called to the intersection of Carmen Road and Buchanans Road, SH1 at 3.23PM.

A St John spokeswoman said they were notified of the motor vehicle incident and responded with two ambulances, two rapid response units and one manager to the scene.

Paramedics have assessed and treated three patients, two in a minor condition and one in a serious condition who have been transported to Christchurch hospital. 

A motorist told Chris Lynch Media one of the vehicles involved was covered in tarpaulin.

NZTA said State Highway One was closed between Yaldhurst Road and Waterloo Road.

Motorists are advised to avoid the area and expect delays.