HOHHOT -- North China's Inner Mongolia autonomous region has shut down nearly 900 coal mines and 2,000 non-coal mines in a seven-year overhaul effort to better preserve resources and protect the local environment, authorities said Thursday.

The region, abundant with coal and other mineral resources such as rare earths, has brought the number of coal mines to about 500 from over 1,300 in 2005, according to the regional department of land and resources.

Thanks to an initiative to merge the region's scattered mines, all coal mines with an annual capacity of no more than 300,000 tons have been ordered to shut down, sources with the department said.

As a result, the average capacity of a single pit has been hiked 10-fold to 1.4 million tons.

Inner Mongolia holds China's largest coal reserves. It surpassed neighboring Shanxi province to become the country's largest coal-producing region in 2010. Its coal output reached 990 million tons last year, rising 25.9 percent from a year earlier, according to statistics from local authorities.