A surfer has been killed by a shark off a notorious stretch of Australia's west coast.

No one saw the incident at a beach near Gracetown, but the surfer's injuries were consistent with a shark attack, police said.

The sleepy community of Gracetown has seen three fatal shark attacks on surfers in the past decade. the latest victim, believed to be in his 20s, was found by a passer-by.

Western Australia state police spokesman Samuel Dinnison said it was not yet clear whether the victim was still alive when he was found or how he got out of the water.

Western Australia fisheries chiefs closed beaches in the area - the state's top surfing and wine-making region - south of Perth.

Marine officers would be sent with shark-catching gear to the surrounding waters as soon as possible, the fisheries department said.

Great white sharks are often responsible for fatalities off Australia's west coast.