One of the world's last Javan rhinos (Rhinoceros sondaicus annamiticus) has been shot and killed by poachers in Vietnam, the World Wildlife Fund said Monday. The animal was shot and its horn, valued in traditional Asian medicine, was cut off.

No one knows exactly how many Javan rhinos remain in the world, but estimates for the population range from 40 to 60 animals, with possibly eight existing in Vietnam's Cat Tien National Park. The critically endangered species is elusive, rarely photographed and almost never observed in the wild. None exist in captivity.

"This is devastating news for rhino conservation and Vietnam," the WWF's Dung Huynh Tien said in a prepared statement.

The WWF is now asking the Vietnam government to launch a criminal investigation into the rhino's death. The species is legally protected in Vietnam, where punishments for killing endangered species can include fines or prison sentences.

Rhino poaching worldwide hit a 15-year high last year as demand for their horns has driven prices up ever higher.

Photo: Rare photo of a Javan rhino, courtesy of WWF.