Three people have died in three separate car crashes across south-east Queensland yesterday.An elderly man died in one incident north of Brisbane after his car drove off a bridge and crashed into a river.

Emergency services were called to Bauple Woolooha Road in Gunidah, about 220km north of Brisbane, after a Subaru Forester had veered off the road and careered into the Mary River.

Members of the public went into the river to try and save the driver, a 71-year-old man, however, police divers eventually found him dead in the car.

It came after two crashes in different parts of the state claimed the lives of two other people.

Emergency services were called to a crash in North Isis, south of Bundaberg, after reports a Holden Commodore and a Nissan X-Trail collided at Childers Road just after midday.

The sole passenger of the Nissan, an 87-year-old woman from Apple Tree, suffered critical injuries and died at the scene.

Police car stock photoPolice are investigating all three fatal incidents. (Getty/Stock Image)

The driver of each car, an 82-year-old man in the Nissan and a 17-year-old boy in the Holden, were taken to Bundaberg Hospital with non-life-threatening injuries.

The other crash involved a Toyota Rav-4 colliding with a tree in Aubigny, just outside of Toowoomba about 1.30pm.

Police arrived on the scene at Oakey Pittsworth Road and found the car, driven by a 74-year-old woman, had left the road.

She suffered critical injuries and died at the scene.

Investigations into all three crashes are ongoing, and anyone with information on he fatal incidents urged to contact police.