Five sperm whales were stranded on a Dutch beach on Tuesday, leading local authorities to urge people to stay away in order not to further distress the giant mammals.

"Five sperm whales got stranded at Texel this afternoon," the municipal authority for the small island in the Dutch northwest said on its internet site.

"Only authorised persons may approach the animals to avoid disturbing them or causing them stress," the statement added.

A whale specialist, cited on public television, said the chances of the whales surviving their ordeal wasn't high.

"The animals have already suffered significant damage.. and two of them are already on their sides," said the expert, Adrie Vonk.

The reasons for the whales getting beached were not known.

The sperm whale is the largest of the toothed whales, and the largest toothed predator. It can measure up to 20 metres (67 feet) long and weigh over 50 tonnes.