A 22-year-old man who was seriously injured in a crash in Merriwa on Sunday night has since died in hospital.

The man was riding a motorbike on Marmion Avenue when it collided with a car at the Greyhound Drive intersection at around 7:30pm.

A 19-year-old woman who was a passenger in the vehicle was also seriously injured.

She remains at Royal Perth Hospital.

Police are appealing for any witnesses to come forward.

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