The extensions - awarded to mines in the regions of Inner Mongolia, Xinjiang and Ningxia, as well as Shanxi and Shaanxi provinces - will help raise coal output by an estimated 150,000 tonnes per day, the National Development and Reform Commission (NDRC) said in a statement.

"It was agreed to extend the ... trial operational time for another year to increase output and supply while ensuring safety," the NDRC said, noting the mines had previously suspended production.

China asked producers in May to hike output to meet peak summer demand as it seems to stabilise prices of the commodity, which have hit record highs this year.

The NDRC earlier on Wednesday said it had issued a notice allowing trial operations at coal mines to be extended - in principle by one year - when their trials expire.

The notice, jointly issued with the National Energy Administration, also requires local government departments to guide and support companies in order to speed up applications for coal mining licences and approve qualified coal mines for trial operations as soon as possible, the NDRC said.

(Reporting by Beijing Newsroom; Writing by Tom Daly; Editing by Mark Heinrich and Mike Harrison)