Though the beast is more closely related to wild cattle, it resembles an antelope with two sharp horns that can reach up to 4 feet (1.2 meters) in length.
The last time a saola was spotted in the wild was 1999, but it hasn't been seen in Vietnam since 1998. In 2010, villagers in the Laos province of Bolikhamxay caught a saola, but the animal died shortly after capture.
WWF conservationists say they are working with Vietnamese partners to protect saolas from illegal hunting.
"Saola are caught in wire snares set by hunters to catch other animals, such as deer and civets, which are largely destined for the lucrative illegal wildlife trade," Van Ngoc said. He added that 30,000 snares have been removed from the saola habitat since 2011 and more than 600 illegal hunters' camps have been destroyed.
"Confirmation of the presence of the saola in this area is a testament to the dedicated and tireless efforts of these forest guards," Van Ngoc said in a statement.
Scientists suspect that no more than a few hundred or a few dozen saola exist in the wild, but they have not been able to come up with a precise population estimate. The species is listed as critically endangered by the International Union for Conservation of Nature.