Researchers digging through mud in northeast India have discovered a new family of legless amphibians in a rare scientific breakthrough detailed in a study released on Wednesday.

The family of burrowing, tailless creatures was identified by scientists working for five years in remote Indian states including Sikkim, Arunachal Pradesh and Nagaland.

"DNA analysis has confirmed that this is an entirely new family," S.D. Biju, a professor at the University of Delhi who led the project with team members from Britain and Belgium, told AFP.

"Habitat destruction is a big problem for amphibians worldwide, and discoveries like this prove that we must protect the environment to save parts of the natural world we know little about," he said.

Biju said that it had been a challenging physical job digging with spades at 250 locations looking for the worm-like creatures, which are about 20 centimetres (eight inches) long and often 25 centimetres deep into the earth.

The new family, the 10th from the caecilian group of amphibians, has been called Chikilidae after the name used by the local Garo tribal language.

"This discovery has shown that northeast India is uniquely rich in wildlife and ecosystems," said Biju. "We have to understand more about the region."

One threat to harmless amphibians in India is from locals who kill them believing they are venomous snakes, the study said.

The findings have published by the Royal Society of London journal Proceedings B.