A rat plague is threatening more than 9 million hectares of grasslands in north China's Inner Mongolia Autonomous Region, local authorities said Monday.

In recent years, some pastures in Inner Mongolia have been overwhelmed by the burrowing rodents, said Zhang Zhuoran from the Inner Mongolia Autonomous Region's Department of Agriculture and Animal Husbandry.

This year's persistent drought and grassland degradation are to blame for the rat plague, as rats are more adaptable to dry weather, Zhang said.

"The rats not only eat the grass but also pull out the roots, which increases the region's degradation," said Vice Director of Bayan Nur Grassland Station Fan Qiang.

In recent times, the local government has resorted to spraying poisons with seed machines and airplanes to combat the rats.

As of Monday, local authorities had mobilized more than 70,000 workers and sprayed over 670 tonnes of poison over 9 million hectares of grassland.