Illegal hunting in Democratic Republic of Congo has wiped out 70 percent of Eastern gorillas in the past two decades and pushed the world's biggest primate close to extinction, a Red List of endangered species showed on Sunday.

Four of six species of great apes are now rated "critically endangered," or one step away from extinction. Threats include hunting, a loss of forests, and farming, from West Africa to Indonesia, according to the annual list by wildlife experts, the world's most comprehensive inventory of plant and animal species.

Eastern gorillas, revised from a lesser category of "endangered", join their sister species, the Western gorilla, and both species of orangutan which were already on the list as critically endangered.