One dead in fatal road collision in SA

South Australian police are at the scene of a fatal car crash in the Riverland that has left one person dead and another with life-threatening injuries.

One person has died after a car hit a tree and then a truck in South Australia's rural Riverland region.

Police and emergency services remain at the scene of the fatal smash that occurred at a Renmark intersection at about 7.30pm on Thursday.

The passenger of the car died at the scene while the driver sustained life-threatening injuries and is expected to be airlifted from the Berri Hospital to the Royal Adelaide Hospital, police said.

The truck driver was not physically injured.

The Sturt Highway has been closed between the Paringa bridge and Renmark Avenue and diversions are in place to divert traffic.