A cyclist has been critically injured in a hit-and-run on a busy Sydney road.

Police say a red car and a pushbike rider collided on Spit Rd in Mosman about 5.15am on Sunday.

The rider was treated by paramedics at the scene before being taken to Royal North Shore Hospital in a critical condition.

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The car did not stop and fled the scene.

“Police from the Crash Investigation Unit examined the scene and have commenced an investigation,” police said.

The bike, a helmet and a pair of cycling cleats were left behind at the scene.

Anyone with any information has been urged to come forward.