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One in five reptiles is threatened with extinction, according to the first major study of more than 10,000 species across the world.

Scientists are calling for urgent conservation action for crocodiles and turtles which are in a particularly bad situation.

They say reptiles have long been overlooked in conservation, and there is more focus on "furry and feathery" creatures.

The study revealed 21% of reptile species are threatened (1,800 individual species).

The number is higher than for birds, but lower than for mammals and amphibians. It also showed that 31 species have already gone extinct.

Reptiles are threatened throughout the world but especially in tropical regions of South-East Asia, West Africa, northern Madagascar and the Caribbean islands at the highest risk.

Habitat destruction from the expansion of farmland, urban development and logging is a big threat, which is why reptiles living in forests were among the most threatened, with 30% of species at risk of extinction.

Crocodiles and turtles also face threats from hunting.

More than half of crocodiles and almost two thirds of turtles are threatened with extinction.

Climate change is also a big threat, particularly on low-lying islands.

Scientists involved in the study, which was published in the journal Nature, said there had been less focus on reptiles than other species when it comes to conservation.

"Reptiles to many people are not charismatic, and there's just been a lot more focus on some of the more furry or feathery species of vertebrates for conservation," said Dr Bruce Young of the international nature organisation, NatureServe.

Speaking at a news conference, the study's authors said there needed to be a global agreement to stop the threat to reptiles.

Neil Cox of the IUCN-Conservation International Biodiversity Assessment Unit said: "The hope is that we can really start making efforts to reverse this extinction catastrophe."