Four serious crashes in six hours across SA at Myponga, Bellevue Heights, Hart and Barossa

Two men have died and a third is fighting for life in separate crashes, while a church filled with worshippers has been badly damaged in a third.

Two men have died in separate crashes on South Australian roads on Tuesday night.

A Seaford Rise man is the 54th death on the state’s roads this year after his car slammed into a tree at Myponga.

Police were called to Main South Rd with reports a white Suzuki sedan struck the tree then caught alight about 9pm Tuesday.

A 75-year-old Seaford Rise man was killed in a crash on Main South Rd at Myponga. Picture: 7NEWS

The 75-year-old Seaford Rise man was the sole occupant of the car and died at the scene.

Fire crews extinguished the blaze and Major Crash officers were called to examine the circumstances.

Authorities shut Main South Rd between Inman Valley Rd and Forktree Rd, and traffic was diverted into Victor Harbor, as investigations got underway.

Roads have since reopened.

In another incident, a 52-year-old man from Hart, in the state’s Mid North, died after he was struck by two vehicles.

The man was a pedestrian on Rail Corridor Rd when police say he was hit by a car and truck about 7pm.

He died at the scene, and is the 53rd death on the state’s roads this year.

Rail Corridor Rd was closed between Hart Rd and Hart Church Rd while Major Crash Investigators were called in. The roads have since reopened.

Meanwhile, in an unrelated incident, a car slammed through a fence and into a church filled with worshippers at Bellevue Heights.

The ClearVision Church on Alpha Rd was extensively damaged but worshippers inside at the time escaped injury in the incident reported about 7pm.

The male driver of a Toyota sedan suffered minor injuries and was taken to hospital.

It is understood the man accidentally hit the accelerator.

The crash destroyed a wall with the church boarded up, and the vehicle was towed from the scene.

The driver is expected to be issued with an expiation notice.

It comes as a man fights for life after a Volkswagen hatchback crashed head-on with a school bus in the Barossa Valley on Tuesday.

That crash occurred at the intersection of Kalimna Rd and Penrice Rd at 3.45pm Tuesday.

And Adelaide Hills commuters should prepare for delays or find an alternative route after at least seven cars collided near the South Eastern Freeway tunnels at Crafers West on Wednesday morning.