A Sao La, one of the rarest large mammals on Earth, was spotted in Vietnam after 15 years without a sighting thanks to remote cameras installed in forests of the Truong Son mountain range in the central Quang Nam Province.

According to the World Wildlife Fund and the Forest Management Department of the province, an animal of the Sao La species, with scientific name of Pseudoryx nghetinhensis, was seen walking along a stream in a small valley on September 7. A live Sao La was last seen in Vietnam in 1998.

It is now thought that as few as a couple dozen and at most a few hundred of the species may exist in forests along the Vietnam and Laos border.

"These are the most important wild animal photographs taken in Asia, and perhaps the world, in at least the past decade," said William Robichaud, coordinator of the Saola Working Group of the International Union for Conservation of Nature's Species Survival Commission, in a press release delivered by the WWF.

Van Ngoc Thinh, WWF-Vietnam's country director, called the pictures ‘a breath-taking discovery,’ saying, ‘we couldn’t believe our eyes when we first saw the photos’.

"We are very happy with the news because the Sao La is considered the ‘holy grail’ of wild animals by conservationists in Southeast Asia,” he added.

The Sao La looks like an antelope and has two closely spaced parallel horns. Because of this, it is nicknamed “the Asian unicorn.”