Police said the 34-year-old male cyclist suffered critical injuries in the crash on the corner of Carlisle and Kurrajong avenues in Mount Druitt about 5pm on Thursday.

The man was taken to Westmead Hospital, but died that night.

Police are still investigating the cause of the crash, but say the cyclist and the bus were believed to be heading east on Kurrajong Avenue when the crash occurred as the bus turned on to Carlisle Avenue.

The male bus driver was not injured in the crash. He was taken to Mount Druitt Hospital for mandatory blood and urine testing, and will be interviewed by police.

There were passengers on the bus at the time, but they were not injured.

The Metropolitan Crash Investigation Unit is investigating the cause of the crash, and officers have seized the bus for examination.

The man's death follows two serious crashes on Tuesday, in Surry Hills and in Tempe.

The first occurred at on the corner of Foveaux and Bellevue streets in Surry Hills during Tuesday morning's peak hour when a cyclist and a garbage truck collided.

The man, aged in his 30s, suffered multiple injuries, including a suspected fractured pelvis and lower limb fractures, and was taken to St Vincent's Hospital in a serious condition.

The same night, another cyclist was critically injured in a crash with a car near a popular sports ground in Tempe.

The 32-year-old man suffered major head and facial injuries in the collision on Holbeach Avenue, next to the Tempe Recreation Reserve.

Police said the cyclist had been riding on the footpath but, when he joined Holbeach Avenue, he was involved in a collision with a Toyota Camry about 8.50pm. Police said he remained in intensive care in hospital on Friday morning.

Anyone with information about the crashes has been urged to contact Crime Stoppers on 1800 333 000 or visit the Crime Stoppers online reporting page.