Australian officials on Thursday began planning the grim task of disposing of almost 400 whale carcasses as hopes faded that there would be many more survivors of one of the world's biggest mass strandings of the mammals.

Rescuers had managed to free around 70 of the long-finned pilot whales beached off the country's remote southern coast by Thursday afternoon. The majority of those freed had reached deeper water, officials said, but four were likely to be euthanized and others might return when the tide turns.

The clock was ticking for the remaining 20 whales still floundering in shallow water on a wide sandbank, four days after the 470-strong pod was first spotted off Tasmania's west coast.

Reuters