A main Southland highway has been blocked in both directions after a three-vehicle crash this evening.

State Highway 6/Winton-Lorneville Highway was closed between Flora Rd West and Orion Rd after the crash, which was reported about 6.40pm.

Police said ambulance crews were at the scene treating people with moderate and minor injuries.

A Hato Hone St John spokesperson said it went to the crash in Makarewa after receiving a call at 6.42pm.

Two ambulances, an operations manager and a critical care unit were sent, treating four patients with minor or no injuries.

Diversions are in place, and drivers are urged to avoid the area while crews clear the site.