A 100 km long fence has been built on the border between the Alxa League of the Inner Mongolia autonomous region and Mongolia to keep out wolves, the Xinhua News Agency reported Monday.

    The fence was built in June by local border police, it said.

    Alxa League shares a 700-km border with Mongolia.

    Bai Wenjun, chief of the border control police with the county-level Alxa Left banner, said there has been an increase in the population of local wolves and those from Mongolia.

    In the past two years, 41 herding families have lost 600 sheep and 300 camels to wolves. The attacks have cost 800,000 yuan ($117,000), Bai said.

    Wolves in Inner Mongolia are growing in number because of a better environment, while increasing human activity in the grasslands of Mongolia are driving the animals across the border, he said.

    One herdsman, Hao Chengrong, has lost more than 90 sheep and camels since March.

    Another, Garima, lost 16 sheep in February and March.

    "Wolves had disappeared from the grasslands for many years, but now they are coming back. This is a problem," she said.

    In the past six years, the league has restored 1.57 million hectares of grassland to improve the environment. One good result is that many rare animals such as the Mongolian gazelle and the Asiatic wild ass have also increased in population