BEIJING, Feb 3 (Reuters) - An explosion killed nine people at a coal mine in northern China, state media reported, just as the government ordered scores of pits to stay open to alleviate the country's worst-ever power shortage.

The blast happened on Saturday at a colliery in the coal-rich province of Shaanxi, the latest in a grim series of Chinese mining disasters.

Its timing highlighted the dilemma faced by Chinese authorities as they seek to ease a crunch in coal supplies that, exacerbated by a harsh winter, has left swathes of southern and central China blacked out.

While ordering major state-owned mines to stay open through the Lunar New Year holidays, officials have said they would not boost output at the cost of safety. China's mines are already the world's deadliest, claiming some 3,700 lives last year alone.

"We must strictly prohibit production that goes beyond abilities, beyond the established limits and beyond the strength of the mine," Huang Yi, spokesman for the State Administration of Work Safety, said on Saturday.

Beijing has been waging a crackdown on unsafe mines, but in the past it has retreated from such campaigns when costs to production started to mount.

Although the mines are small, analysts say the loss of their output does add up.

Even before the bad weather hit, power plants in several Chinese provinces were already running short of coal, because a huge rise in coal prices had not been matched by an increase in electricity tariffs.

Ma Kai, the country's top economic planner, last week urged small mines to step up their coal production so long as they complied with safety standards.

The freak weather, which could last another week, meant that more than 3,500 mines in hard-hit provinces have suspended production, authorities said on Saturday.

Mines normally stop production for up to three days over the New Year for maintenance work and to allow miners to go home for the holiday, but this year the government has cut that back to one day and some companies have vowed to take no break at all. (Reporting by Simon Rabinovitch; Editing by Sanjeev Miglani)

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