Major Crash officers are investigating a motorcycle crash that left a man in a critical condition in Halls Head on Saturday evening.
About 8.30pm, the driver was involved in a police pursuit throughout Mandurah and Halls Head and crashed along Old Coast Road near the McLarty Road and Leeward Entrance roundabout.
The road was blocked in both directions as officers probed the scene.
The wreckage of the rider's black Harley Davidson motorcycle was strewn across grass on the eastern side of the roadway.
The RAC rescue helicopter was called in to convey the injured man, in his 20s, to Royal Perth Hospital and landed at the nearby Peelwood Parade Oval.
St John Ambulance transferred the man to the oval and attempted to stabilise him while crews prepared the helicopter.
About 10.45pm, the man was finally airlifted from the southern Mandurah suburb.
Two lanes of Old Coast Road remained blocked off by police as the authorities dealt with the situation overnight.
Motorists were advised to avoid the area.
Police will allege the pursuit began in Mandurah along Pinjarra Road.
Officers then followed the man along Sutton Street, Davey Street, George Street, Pinjarra Road and Old Coast Road, where he crashed near the McLarty Street intersection.
Major Crash Investigators are seeking witnesses who may have seen the crash or the motorcycle beforehand.
Police are particularly interested in dash cam footage of the motorcycle.
People with information are urged to call Crime Stoppers on 1800 333 000 or make a report online at www.crimestopperswa.com.au.