Recent sightings of wild Siberian tigers in northeast China have encouraged wildlife experts to call for China to expand its natural reserves for the endangered animals.

An infrared camera set up by the World Wildlife Fund (WWF) and forestry authorities in northeast China's Jilin Province has captured images of a wild Siberian tiger in the Wanda Mountains.

Siberian tigers are among the world's rarest species. The population of the species is estimated to be around 500, most of which live in east Russia and northeast China. China is thought to have approximately 20 Siberian tigers living in the provinces of Heilongjiang and Jilin.

China established the Huichun Nature Reserve, located near the Sino-Russian border, to protect Siberian tigers in 2001. However, the tigers have been seen expanding from border areas to the northeastern interior in recent years.

"The increasing number of wildcat sightings can be considered evidence of progress in China's efforts to protect the animal," according to Zhu Jiang, director of the Northeast China Program Office of the World Wildlife Fund (WWF).

"The tigers are now inhabiting a wider territory, so natural reserves for the tigers should be expanded accordingly," Zhu said.

"The Chinese government should endeavor to eliminate potential threats to the safety of the tigers, such as animal traps," said Zhu Chunquan, a director in charge of bio-diversity protection and implementation at WWF China.

A WWF survey found an average of 1.6 traps for every 10 km of area in Heilongjiang's Siberian tiger nature reserves in Heilongjiang and Jilin last winter.

"The WWF hopes to cooperate with local governments to protect Siberian tigers and restore their habitat. We aim to double the population of wild Siberian tigers in China by 2022, " Zhu Jiang said.

Local governments in Jilin and Heilongjiang are working on policies that will help establish new nature reserves, as well as stronger measures for the protection of the species.

Jilin plans to build ten nature reserves for Siberian tigers by 2020, and about 632 local households will be relocated to make room for the reserves, according to the province's forestry department.

"We are planning to build two new reserves for the tigers in order to create favorable conditions for the protection and repopulation of the species," said Dong Jie, vice director of Heilongjiang's Forest Industry Bureau.