An Australian surfer was attacked and killed by possibly two sharks off the west Australian coast on Saturday, said a fisheries official.

The surfer in his late 20s was attacked while surfing a break called "Left-Handers" near one of Australia's most famous big wave surf spots, Margaret River, 200 kilometres south of Perth in the state of Western Australia.

"The man suffered a large bite to the legs and torso," a Western Australia police spokesman told reporters.

One witness told Australia's Sky News that two teenagers who pulled the victim out of the water said the shark was "as big as a car". The Western Australian Department of Fisheries was investigating whether two sharks could have been involved.

"It looks as though there may have been two animals involved," a fisheries spokeswoman told reporters."

The St John Ambulance Service at the small fishing village of Gracetown said it was alerted to the mid-afternoon shark attack by a witness standing on the beach.

There had been a number of recent shark sightings along the Margaret River coast but none in the vicinity of the attack.

Left-Handers is a long beach, often deserted, lined with a rocky shelf which is pounded by large ocean swells out of the southern Indian Ocean. The beach has been closed.

The first documented shark attack in Australia occurred in 1791 and there have been 625 shark attacks in the past 200 years, 187 of them fatal, according to the Australian Shark Attack File kept by Sydney's Taronga Zoo.

The last fatal shark attack in Western Australia was in 2000 off Cottesloe Beach in the city of Perth when a Great White attacked a bodysurfer only a few metres off the beach.

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