A man aged in his 40s has been taken to hospital in a critical condition after he was crushed by a large rock while undertaking excavation work on a river bank.

The Mounties Care CareFlight Helicopter was tasked by NSW Ambulance shortly after 11:30am to Penrith and landed in a park near the scene.

CareFlight’s specialist doctor and NSW Ambulance critical care paramedic joined NSW Ambulance crews on scene who had provided initial treatment.

Fire and Rescue NSW used air bags to lift the several hundred kilogram rock to free the man.

CareFlight’s critical care team conducted a clinical assessment, including ultrasound to assess the man’s internal injuries.

The man was taken in a road ambulance under ongoing treatment from CareFlight’s critical care team, including blood transfusions to stabilise the man. He was taken to Westmead Hospital in a critical condition.