China is scrambling to deliver more coal to utilities to restore supply, as nearly two-thirds of Chinese provinces struggle with power rationing. The three northeast provinces of Liaoning, Heilongjiang and Jilin - home to nearly 100 million people - have been particularly hard hit.

Inter RAO, which received a request from the State Grid Corporation of China to increase electricity supplies to the country's northern provinces this week, started to increase exports on Friday, the company told reporters.

In October, its exports to China will rise by 100% year-on-year and by 90% from the original plan for this month, the Russian company said.

All three Russia-China transmission lines, which are capable of delivering up to 7 billion kilowatt-hours of electrical power per year, will be used for supplies, it added.

A top official of China's state-asset regulator said on Friday the country's power supply situation remains challenging and urged grid firms to prioritise residential use and ensure safe operation as winter approaches.

Coal fuels about two-thirds of China's power generation.

Inter RAO exported 3.06 billion kilowatt hours to China last year.

(Reporting by Anastasia Lyrchikova; editing by Susan Fenton)