WELLINGTON- More than 20 pilot whales died in a mass beaching in New Zealand Sunday while another 40 were successfully herded back to sea, conservation officials said.

About 63 whales were stranded on the Coroman del Peninsula on the east of North Island.

Department of Conservation staff assisted by hundreds of volunteers managed to help most of the whales back out to sea during the afternoon high tide at Colville Bay but a spokesman said 21 died on the beach.

People were working to bury the dead whales when the tide went out, Newstalk ZB reported.

However, there was also a fear the surviving whales might try to return to the beach on the next tide and conservation workers were to keep an overnight watch on the area.