By Alex Kirby BBC News website environment correspondent

Sumatran tigers are the smallest sub-species

They fear the hunters, meeting on 12 December close to a tiger sanctuary, may kill some of the protected animals.

They believe two tiger cubs whose skins were seized recently in the district had been killed by people hunting pigs.

The Sumatran tiger is listed by the World Conservation Union as critically endangered, with under 400 individuals.

Tourism 'boost'

Fauna and Flora International (FFI), based in Cambridge, UK, says the pig hunting association plans to take up to a thousand men and dogs into an area adjoining one of the most important tiger sanctuaries in the world.

Sibling skins: Pig hunters are blamed

Although the area designated for the hunt is outside Sumatra's Kerinci-Seblat National Park borders, FFI says the event will put at risk tigers, Asian golden cats, clouded leopards, Malay tapir, sun bears and at least four deer species.

The association, called Porbi, is hoping to hold not only a mass pig hunt but a demonstration of pig baiting with dogs as well, at a festival in Kerinci district intended to promote the area as an eco-tourism destination.

Rusdi Fachrizal, a Sumatran conservationist working on tiger conservation in Kerinci, said: "We are very unhappy about this.

"The case of the two tiger cubs shows that pig hunters are operating outside the rules and without control.

"We do not think that encouraging big organised pig hunting and pig baiting is going to help develop nature tourism in Kerinci.

"For so long as the hunting groups are not supervised and do not operate within the guidelines, they are a threat to rare animals in and around the national park."

FFI says the skins of the two cubs, who were siblings, were seized recently in a joint operation by national park and Kerinci district police officers.

Telltale deaths

They were acting on information from an undercover investigation by the park's tiger protection team.

Poaching is a big danger

FFI says examination of the skins showed the cubs had died in a frenzied attack by five or more men armed with spears and machetes.

It says these injuries were consistent with the killing being carried out by pig hunters. An eyewitness to the killing has also confirmed that this was what had happened.

The skins had been concealed in the house of a Kerinci police officer and were on sale on the black market for $550 each.

The Sumatran is the smallest of the six sub-species of tiger. The animals are at risk from poaching for their skins and body parts for use in Chinese traditional medicine, and from habitat loss.

This leads to conflict as they increasingly encounter people and their livestock. Over-hunting by people of their prey species, such as deer and wild pigs, also raises the likelihood of conflict, as they are forced to take livestock for food.