Australian authorities were yesterday hunting a killer shark which fatally mauled an American diver off the country’s west coast as they considered a cull of the giant marine predators.

The US citizen, 32 and reportedly from Texas, was brutally savaged by what was believed to be a three-metre great white shark during a dive off Perth’s Rottnest Island on Saturday.

Witnesses saw a flurry of bubbles before the man’s body surfaced with horrific injuries.

It is the third fatal shark attack off the west coast in two months.

Fisheries officials said a kill order was immediately issued for the shark and six bait lines had been laid in the vicinity of the attack hoping to catch the creature responsible.

Western Australia Premier Colin Barnett said he would consider a shark cull, as well as greater patrols, aerial surveillance and netting off of beaches and boosting the number of sharks fishermen were allowed to catch.

“There’s a lot of anecdotal evidence about the numbers of sharks increasing,” said Mr Barnett.

“Culling could be considered if those sharks are staying around popular beach swimming areas.”

But the premier said sharks were “natural predators” and though he was very concerned at the surge in fatalities there was little that could practically be done. “I think most people who fish and dive understand this is the domain of marine life and the shark is the top predator,” he said.

“All West Australians really need to take special care in going to the beach and swimming, particularly if they go diving,” he added.

Conditions on Saturday were overcast and still – considered prime shark attack weather.

Swimmer Bryn Martin, 64, was thought to have been taken by a great white, also known as a white pointer, two weeks ago after vanishing off Perth’s Cottesloe Beach.

His bathing suit was discovered on the sea bed with marks consistent with a white pointer attack.

It followed the savaging of bodyboarder Kyle Burden, 21, at the popular west coast tourist spot of Bunker Bay early last month.

Mr Burden was so badly mauled the lower half of his body was torn away, and a great white was again believed responsible.

Sharks are a common feature of Australian waters but fatal attacks are rare, with only 24 recorded deaths in the 20 years up to June 2009, or an average of just 1.2 shark-related deaths per year according to official data.

Popularised by the horror film Jaws, great white sharks are large, rare marine predators which can grow to longer than 6.4 metres.