China became the world's largest coal importer last year, and its thermal power plants generate 70 percent of the country's electricity.

Experts noted, however, that China faces huge environmental issues, and its coal imports might not increase significantly in the coming years.

"China's own coal production has grown rapidly in recent years, and its domestic market was glutted when electricity demand slowed sharply last year," said Chen Yafei, vice-director of the Beijing Research Institute of Coal Chemistry at the China Coal Research Institute.

"But our demand for high-quality coal such as coking coal is huge, because of its high efficiency and energy-saving properties."

Chen said declining demand for coal in Russia and other parts of Europe, the result of coal-fired plants closing to meet tighter environmental standards, is compelling Russian sellers to focus increasingly on Asia, especially China.

Domestic demand in Russia decreased 14 million tons, or by 7 percent, in the past five years, media reports have said.

"Russia has too much of its coal going to China, but it has to be competitive with coal from Indonesia and Australia," he said.

Russian coal does have some advantages, such as lower transport costs and the ability to use rail lines to move large quantities, Chen said.