A multi-vehicle crash has closed State Highway 1 near the Manawatū-Whanganui town of Marton and left two people injured.

Police said emergency vehicles were responding to a report of a two-vehicle crash shortly after 2pm.

Hato Hone St John said they were notified of an incident in Marton at 2pm and sent two ambulances, a rapid response unit, a helicopter and a PRIME unit in response.

One person in moderate condition was treated at the scene, and another person in serious condition was driven to Whanganui Base Hospital.

The road has been closed and diversions put in place.

Police advised motorists to avoid the area and expect delays.