A serious three-vehicle crash has closed State Highway 1 in both directions south of Ward in Marlborough this afternoon.

Emergency services were called to the scene around 2:50pm.

Initial reports indicate that one person has sustained critical injuries, while two others have suffered minor to moderate injuries.

St John confirmed that two ambulances and an operations manager responded to the incident.

One patient in moderate condition is being transported to Wairau Hospital, while another with minor injuries was treated at the scene, a spokesperson told Chris Lynch Media.

The Serious Crash Unit is attending to carry out a scene examination, and police say the road is expected to remain closed for some time.

Motorists are advised to avoid the area or delay travel where possible.