Eleven rare Siberian tigers have died at a cash-strapped zoo in China, heightening concerns about conditions at wildlife facilities in the country.

The tigers were reportedly starving and kept in small cages.

The tigers died in the past three months at Shenyang Forest Wild Animal Zoo, located in the country's cold northeast region, officials and state media said Friday.

These Siberian tiger cubs are among an estimated 50 or fewer tigers left living in the wild in China. (Jacky Chen/Reuters)

Reports said the tigers had been fed nothing but chicken bones and starved to death. A zoo manager said unspecified diseases killed the animals during the harsh winter.

Siberian tigers are one of the world's rarest species. There are an estimated 300 left in the wild, of which 50 are in China. About 5,000 are held captive on farms and wildlife parks across China.

Tiger numbers dwindling

The deaths underscore the conflicting signals in China's attempts to save its dwindling number of tigers. While extensive conservation efforts are underway, animal protection groups say zoos and wildlife parks may be deliberately breeding more animals than they can afford, hoping to sell off the carcasses onto a black market where tiger parts fetch a high price for use in traditional medicines and liquor.

"We've seen cases where zoos have steeped the bones from their deceased tigers in liquor to sell to visitors," said Hua Ning, project director for the China branch of the International Fund for Animal Welfare.

Zoo spokesman Wu Xi however insisted the animals died from "various diseases" that were hard for them to endure because of this year's unusually harsh winter. He said the tigers were kept in cages indoors because of the bitter cold.

Wu wouldn't specify what diseases the animals had.

A zoo official denied there were plans to sell the animals' body parts.

China banned the sale of tiger parts and the use of tiger parts in Chinese medicine in 1993, imposing stiff sentences on offenders, but tiger bone, penis, pelts and other parts are still sold illegally to consumers – some who believe the products increase potency or can cure ailments from convulsions to skin disease.