A pod of 39 pilot whales have died after becoming stranded on a remote New Zealand beach.

The whales, which were beached in Golden Bay on the country's South Island, died on Monday after being spotted near the shore a day earlier, conservation officials said.

It was unlikely they could be rescued.

John Mason, Golden Bay conservation services manager

Rangers had been monitoring the whales but were powerless to stop them from becoming beached, the Department of Conservation said.

Twelve of the whales died naturally and the rest were euthanised after rangers determined they were too far up the beach to be refloated.

"We carefully weighed up the likelihood of being able to refloat them and get them safely back out to sea," Golden Bay conservation services manager John Mason said.

"But our staff, who have extensive experience in dealing with mass whale strandings in Golden Bay, determined that due to various factors it was unlikely they could be rescued," he said.

Mass pilot whale strandings are common in New Zealand, but scientists are not clear on why the marine mammals swim ashore in large groups.

The 39 whales were first spotted in shallow waters off Abel Tasman National Park on Sunday afternoon, but the Department of Conservation said high winds prevented boats from being sent out to herd them out of danger, according to a report from Radio New Zealand.

Source: Agencies