It is one of the rarest animals in the world, a horned beast sighted so rarely it is nicknamed "the Asian unicorn".

So when villagers in a remote region of Laos became the first people in a decade to spot a saola they were keen to keep the antelope-like creature, which has large white streaks of fur that look like eyebrows.

But in their enthusiasm to protect it they may have killed the animal. It died last month after a few days in captivity, conservationists said.

The critically endangered mammal is found in the mountains of Vietnam and Laos. It was discovered in 1992.

The saola looks similar to the antelope of North Africa but is more closely related to wild cattle and is likened to the mythical unicorn because of its rarity.

It has never been seen by conservation experts in the wild and the last confirmed sighting was from automated cameras in 1999.

The species is listed as critically endangered, with just a few hundred thought to exist in the wild. There are none in zoos and almost nothing is known about how to keep them in captivity, meaning if they vanish in the wild they will be extinct.

The Lao government said villagers in the country's central province of Bolikhamxay captured the saola in late August and brought it to their village.

When news of the capture reached the authorities a team was sent, advised by the International Union for Conservation of Nature and Wildlife Conservation Society (WCS) to examine and release the animal.

But the adult male saola died shortly after the team reached the remote village. It was photographed while still alive.

The IUCN's saola expert William Robichaud said:

"We hope the information gained from the incident can be used to ensure that this is not the last saola anyone has a chance to see."

The provincial conservation unit of Bolikhamxay province said the animal's death was "unfortunate" but the incident confirmed an area where it was still found and the government would immediately strengthen conservation efforts there.

Dr Pierre Comizzoli, a member of the IUCN saola working group, said study of the animal's carcass could yield some good.

"Our lack of knowledge of saola biology is a major constraint to efforts to conserve it. This can be a major step forward in understanding this remarkable and mysterious species."