The carnivorous mammal, slightly larger than a domestic cat with dark red fur and a long bushy tail, was caught by an automated camera at night twice in 2003 on the Indonesian side of the island, the WWF said in a press release.

Photos of the animals have been shown to locals well acquainted with wildlife in the densely forested area and the organisation also consulted several Bornean wildlife experts but none recognised it.

"Most were convinced it was a new species of carnivore," WWF said, adding that researchers were hoping to set cage traps to catch a live specimen.

The WWF says it is extremely rare these days to discover a new mammal species of this size, particularly a carnivore.

If confirmed, it would be the first time in more than a century that a new carnivore has been discovered on the island, which lies between the Indian and Pacific Oceans, it added.

The animal, which has very small ears and large hind legs, was spotted in the Kayan Mentarang national park in the mountainous jungles of Kalimantan, where vast tracts of rainforest still remain.

The group warned however that plans by Indonesia announced in July to create the world's largest palm oil plantation in Kalimantan, along the border with Malaysia's Sarawak and Sabah states, threaten further new discoveries.

The scheme, funded by the China Development Bank, is expected to cover an area of 1.8 million hectares (4.4 million acres) and may have devastating environmental consequences, it said.

Environmental watchdogs have criticized the plan, arguing that the jungle soil in the area was infertile and that the elevation was unsuitable for palm oil.

Indonesia is losing at least 2.8 million hectares of its forests every year to illegal logging alone.

The forestry ministry's director for protected areas, Banjar Laban, told AFP that the potential discovery of a new mammal emphasised the urgent need to protect the biodiversity of Borneo's forests.

"If it turns out to be truly a new mammalian species, this should really become a national pride, something that the entire nation should be proud of and work to preserve," he said.

Laban said that the Kayan Mentarang protected forest straddling Central and East Kalimantan was a vast source of biodiversity with 361 new species -- plants, insects, fish and other animals-- discovered between 1994 and 2004.

"But this forest especially along the border (with Malayisa's Sarawak and Sabah) is under threat from illegal logging, the encroachment of logging trails inland and of other human activities," he said.

The discovery of a new species "should lead to a better appreciation of the forest, by the government at all levels as well as the population," he added.

Rapid deforestation has had devastating environmental consequences for both Indonesia and the Southeast Asian region, causing floods and landslides and shrouding nearby countries with haze from illegal fires set to clear land.

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