Six people have been injured in a road crash in Canterbury.

Police say two cars have collided on State Highway One at its intersection with Orari Station Road near Geraldine, north of Timaru.

Two people seriously injured have been flown to Christchurch Hospital while four others have moderate injuries.

The highway remains partially closed with diversions in place.

Traffic is very heavy in the area because of the crash and it's very slow going for motorists, with a stop/go system in place and major delays.

It happened around 11.45.

The crash comes just hours after two people were killed in a two-car crash on the Waimate Highway near Glenavy.

St John says the driver of each car in the Glenavy crash is dead.

The holiday road toll stands at seven.