Authorities said they believed three of the huge mammals, up to 10 metres (33 foot) long and weighing 20 tonnes, were still alive after being badly slashed as waves drove them over the razor-sharp reef.

David Mell from the Western Australia department of Conservation and Land Management department (CALM) said a fisherman spotted the whales Thursday morning at Doubtful Island Bay, about 350 kilometres (217 miles) south-east of Perth.

Mell said blood from the whales' cuts was likely to attract sharks in the area known as a haunt for white pointers, making it too dangerous for wildlife officers to enter the water to try to help them.

"As the animals have been washed over the reef, they are severely lacerated," Mell said. "Consequently, this is likely to attract predators such as sharks, making any rescue attempt exceedingly dangerous."

He also said wildlife officers could do little but leave the whales to their fate as sperm whales were notoriously difficult to put down.

TERRA.WIRE