China's biggest electricity provider has asked the government to help ensure coal supplies and avert a looming power crisis, state media reported on Wednesday.

The State Grid Corp issued the call for help after stockpiles of coal, which provide about 70 percent of China's power needs, had dwindled to a week's supply in recent days, the China Business News said.

The supply crunch was caused by soaring demand due to recent cold weather and heavy snowfalls in parts of the country that have disrupted coal distribution, it said.

Other factors, however, include the recent closure of thousands of coal mines due to safety concerns, and rising petrol costs that have further crimped coal distribution.

About 70 percent of all coal deliveries are made by truck, the paper said.

The looming crisis had already caused 13 provincial power grids in central and southern China to impose restrictions on electricity use, it added.

The government's National Reform and Development Commission has responded to the power grid's plea with a promise to ensure adequate coal supplies by banning all coal deliveries not related to power generation.

China's electricity consumption has soared amid booming economic growth, putting the government in a quandary about how to meet that demand while simultaneously limiting consumption of heavily polluting coal.

According to the State Grid, the national stockpile of coal for power use stood at 17.7 million tonnes on January 20, down more than 40 percent from a year earlier, about an eight-day supply, the paper said.