Five people are injured - one critically - after a crash in southern Waikato

Police say they were alerted to the crash on State Highway 30 near Kopaki just before 7pm.

Hato Hone St John says three others are in a serious condition and one is in a moderate condition.

A spokesperson says two ambulances, a helicopter, and a rapid response unit are at the scene, with two more helicopters en route.

A five kilometre stretch of the highway is closed between Kopaki and Marae-kowhai.