Sumatran elephants in the wild face extinction in less than 30 years unless there is an "immediate moratorium" on destruction of the animals' habitat, environmental group WWF warned on Tuesday.

There are now between 2,400 and 2,800 of the elephants left in the wild on the Indonesian island of Sumatra, which means the population has halved since 1985, said the WWF.

The International Union for Conservation of Nature (IUCN) has also changed its classification of the Sumatran elephant from "endangered" to "critically endangered" on its list of threatened species, said the WWF.

The elephant joins a growing list of critically endangered species on Sumatra, including the orangutan and rhino.

"An immediate moratorium on habitat conversion is needed to secure a future for Sumatran elephants," the WWF warned in a statement.

"Scientists say that if current trends continue, Sumatran elephants could be extinct in the wild in less than 30 years."

It attributed the decline largely to habitat being deforested and converted for agricultural plantations.

The IUCN said it changed its classification because the creature, the smallest Asian elephant, has lost nearly 70 percent of its habitat and half of its population in one generation.

Despite the elephant being protected under Indonesian law, 85 percent of its habitats are not safeguarded as they are outside officially protected areas, according to the IUCN.

This means they are likely to be converted for other uses, said the IUCN.

Elephant numbers in Sumatra's Riau province alone have declined by 80 percent in less than 25 years due to rapid deforestation by pulp and paper industries and oil palm plantations, the WWF said.

"The Sumatran elephant joins a growing list of Indonesian species that are critically endangered, including the Sumatran orangutan, the Javan and Sumatran rhinos and the Sumatran tiger," said Carlos Drews, director of WWF's global species programme.