Story highlights Online campaign launched to save bear sanctuary in Vietnam from closure

Sanctuary provides home for rescued Asiatic black bears

Bile from live bears extracted and used as traditional medicine

Appeal to Vietnam's prime minister to stop center's closure

Wildlife lobbyists are mounting an online campaign to urge Vietnam's prime minister to reprieve an animal sanctuary threatened with closure.

Comic actor Ricky Gervais and broadcaster Stephen Fry are among the many people who have used Twitter to call on Vietnam to lift the threat to shut the Bear Rescue Center, operated by Hong Kong-based charity Animals Asia.

The centre was set up to provide a safe home for bears previously captured and exploited by farmers as a source of bear bile -- regarded as a traditional medicine by many people in east Asian countries.

Bears in the illegal bile industry can be held for decades in cramped cages, having their bile regularly extracted direct from their abdomens in conditions described as barbaric by animal welfare campaigners.

Animals Asia says it's operating on land allocated by the government in 2005 for the purpose of a bear sanctuary, in Tam Dao National Park north of Hanoi. It now houses 104 rescued Asiatic black bears -- also know as moon bears, for their crescent-shaped chest markings.

The charity says it has been told the center has to leave the site after coming under pressure from the director of the national park. It claims he lobbied the Ministry of Defense to declare the area is of national defense significance -- a status the charity says is not justified. It alleges the true motive for reclaiming the land is to develop it for profit.

"We are desperate to ensure that the rescue center is not closed down and relocated," said Jill Robinson, the founder and chief executive of Animals Asia. The charity says it has invested $2 million of donors' money in the bear rehabilitation center, which will be lost if the centre closes. Robinson said it would also cost 77 local people their jobs, and added: "The welfare of 104 bears, who have already suffered enough, would be seriously compromised."

Now she and Animals Asia are pinning their hopes for a reprieve on an appeal to Vietnamese Prime Minister Nguyen Tan Dung. They say he can override the eviction ruling, and are urging him to honor the original agreement to set land aside as a home for bears.

Stephen Fry this week joined the campaign to stop the sanctuary from being shut, tweeting to his 4.9 million followers: "Stop 104 rescued bears losing their home! Email Vietnam's PM to save Animals Asia's sanctuary #stoptheeviction ".

The government of Vietnam has so far not responded to CNN's requests for comment.