A cyclist has died in hospital after colliding with a bus in western Sydney.

The 34-year-old man collided with a bus at Mount Druitt just after 5pm on Thursday (AEST), police said.

He was taken hospital in a critical condition and died there.

The male bus driver, who was not injured, was taken to Mount Druitt Hospital for blood and urine testing and is being questioned by police.

Meanwhile, an elderly man died earlier on Thursday after a single-vehicle crash in northwest NSW.

The 81-year-old’s car reportedly drove down an embankment off the Gwydir Highway, about 40km east of Glen Innes, and crashed into bushland about 3pm (AEST).

He died at the scene.