The okapi, a zebra-like relative of the giraffe and national symbol of the Congo, is now considered endangered, according to the International Union for Conservation of Nature and Natural Resources (IUCN), which released its twice-yearly update of its seminal Red List of Threatened Species.

The revised list also reflected the further endangerment of the sub-Saharan white-winged flufftail -- one of Africa's rarest birds. The IUCN said both endangered species are "on the brink of extinction."

Sometimes referred to as forest giraffes, okapi (Okapia johnstoni), the IUCN said, are unique to the rainforests of the Democratic Republic of the Congo (DRC) and threatened to a great extent. Okapi's new position as "Endangered" on the Red List is the third most dire position a living species can hold, behind "Critically Endangered" and "Extinct in the Wild."

The IUCN said that okapi populations have been declining since at least 1995 and that the trend is expected to continue. The rate of decline is believed to have been in excess of 50 percent over three generations of the mammals (24 years).

"The okapi is revered in Congo as a national symbol -- it even features on the Congolese franc banknotes," said the Switzerland-based IUCN's Noëlle Kümpel, an okapi specialist. "Sadly, DRC has been caught up in civil conflict and ravaged by poverty for nearly two decades, leading to widespread degradation of okapi habitat and hunting for its meat and skin. Supporting government efforts to tackle the civil conflict and extreme poverty in the region are critical to securing its survival."

Militant groups of Congolese in and around key protected areas pose the greatest threat to the okapi, the IUCN said.

"These groups prevent effective conservation action, even surveys and monitoring in most sites, and engage in and facilitate elephant poaching, bushmeat hunting, illegal mining (gold, coltan and diamonds), illegal logging, charcoal production and agricultural encroachment. In a notorious incident in June 2012, armed rebels attacked the [Okapi Wildlife Reserve] and killed seven people and all 14 captive okapi."

Although new endangered species were added to the Red List, the IUCN reports gains on other fronts. The leatherback turtle has seen a recovery and is now listed on the Red List as "vulnerable," revised from "critically endangered." California's island fox and two albatross species have also recovered, the IUCN said.