A tourist is fighting for life following a bicycle accident on Rottnest Island, offshore of Western Australia.

Emergency crews responded to calls about 5pm on Tuesday that an overseas tourist had fallen from a bicycle on Digby Drive in the Thompson Bay area of Rottnest Island.

They found a 38-year-old woman suffered life-threatening head injuries following the fall.

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She was flown from the island to Royal Perth Hospital in a critical condition.

The circumstances surrounding the crash remain under investigation.

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