China Coal Energy Co, a unit of the nation's second-biggest producer of the fuel, rose by the most in more than 19 months in Hong Kong on Wednesday after the company reported a 7.8 percent gain in its first half profit.

Shares gained 6.9 percent to HK$10.04 at the close in Hong Kong. It was the biggest one-day gain for the stock since January 5, 2010.

China Coal's net income was 5.6 billion yuan ($876 million) in the six months ended June 30, compared with a restated profit of 5.2 billion yuan a year earlier, according to a statement filed to the Hong Kong Stock Exchange on August 16 after trading had finished. That beat the estimate of Bank of China International Holdings Ltd's Lawrence Lau, which he wrote in a note on Wednesday. He raised his recommendation to "buy" from "hold."

The company boosted coal sales by 9.7 percent during the period. Revenue gained 19 percent as coal prices remained high, it said.

Operating profit in the current half would "at least stay at the same level of the first half", Chairman Wang An told reporters in Hong Kong on Wednesday. Profit from operations was 8.1 billion yuan in the first half.

Still, slower economic growth in China may cut coal prices in the second half, he said.

The company may boost annual coal production to 200 million metric tons by 2015 through expansion and by acquiring mines from its parent group, he said. Its output last year was 94.4 million metric tons.