Coal exports soared 83.5 percent year-on-year in June to 6.99 million tonnes, the highest monthly total since March 2005, the General Administration of Customs said on Thursday.

Analysts said the surge likely reflected a widening gap between higher world prices and domestic prices, which are capped by the government. The gap was about 54.70 U.S. dollars per tonne in the week ended on July 4, the China Business News reported on Thursday.

Rising exports would exacerbate shortages at coal-fired power plants, which were striving to ensure electricity for the Olympics and reconstruction from the May 12 quake, analysts said.

To protect power plants' profits, the government has imposed temporary controls on the factory prices of thermal coal, capping them at the price that prevailed on June 19, which is effective through the end of the year.

Coal exports totaled 25.49 million tonnes in the first half of 2008, up 10.2 percent year-on-year, according to the administration.