Villagers in western Indonesia speared to death three Sumatran tigers this month after the critically endangered cats strayed from protected forests to attack livestock and killed six people in a neighboring province, a conservationist said Tuesday. The endangered tigers were killed in Riau, a province on Sumatra island, said Samsidar, a spokesman for the WWF who like many Indonesians uses only one name. Residents in Indragiri Hilir district caught and speared the first tiger on Feb. 10 and the other two on Feb. 16, he said, adding that wildlife officials suspect the skins of the dead cats may have been sold to poachers. «We haven't been able to find their carcasses,» he was quoted as saying by Associated Press. Sumatran tigers in neighboring Jambi province mauled to death six people in the last month, prompting conservationists to launch a massive operation to capture and relocate the animals. There are only around 250 of Sumatran tigers left in the wild, compared to about 1,000 in the 1970s, according to the WWF. As a result, their subspecies, Panthera tigris sumatrae, could become the first large predator to go extinct in the 21st century.