The toads of Altona are dying in their thousands

Thousands of the amphibians have died in recent days in a pond in Hamburg's Altona district, with their bodies swelling to bursting point.

The toads' entrails are propelled for up to a metre (3.2ft), in scenes that have been likened to science fiction.

Scientists are baffled. Possible explanations include a unknown virus or a fungus in the pond.

"You see the animals crawling on the ground, swelling and then exploding," German conservationist Werner Smolnik told AFP news agency.

The bodies of the toads expanded to three and a half times their normal size, he said.

"I have never seen such a thing," AFP quotes veterinarian Otto Horst as saying. The site - which has been dubbed "the pond of death" - has been closed to the public.

The exploding toads have also crossed the border north into Denmark, according to Danish Radio.

It reported that a large number of toads that live in a pond near Laasby in central Jutland have started to suffer the same fate as the German amphibians.

The toads crawl onto the land, swell up and explode in the middle of the night, the radio said.