Australian authorities on Sunday continued hunting for a killer shark that mauled to death an American recreational diver off Australia's southwest coast a day earlier.

Two friends of 32-year-old George Wainwright, from Texas, said he was savaged by a three-meter-long great white shark during a solo dive just off Perth's Rottnest Island. They said they watched in horror as Wainwright's body surfaced near their boat just moments after they saw a flurry of bubbles arising on the surface.

Australian Fisheries Minister Norman Moore immediately issued an order allowing for any shark considered a threat to human life to be hunted down and killed. Local authorities also ordered all beaches in the area closed.

Police said Wainwright had been in Australia for several months on a work visa.

Saturday's attack was the third in the area since early September. A great white of the same size is believed to have taken a 64-year-old Australian swimmer off Perth's Cottesloe Beach on October 10. The man's remains were never found, but his shredded bathing suit was discovered on the sea bed.

In early September, a 21-year-old body boarder was mauled at a beach south of Perth. A great white was again believed responsible.

Although sharks are a common feature in Australia, fatal attacks on humans are rare.