HONG KONG, May 22 (Reuters) - China shares ended slightly lower on Thursday, as a sell-off in coal stocks outweighed earlier gains helped by a preliminary private survey showing the best performance of the country's factory sector in five months in May.
The Shanghai Composite Index ended down 0.2 percent at 2,021.29 points. The CSI300 of the leading Shanghai and Shenzhen A-share listings also inched down 0.2 percent.
China's gas-related stocks were buoyed by a long-awaited gas deal between China and Russia, expected to help stabilise gas supply and prices on the mainland.
Changchun Gas Co Ltd surged the maximum allowed 10 percent in Shanghai, while Shenzhen Gas Corp Ltd jumped 5.5 percent.
But the coal sector which was a big index boost on Wednesday suffered losses facing competition from cleaner energy, with Yanzhou Coal Mining Coal Ltd down 2.0 percent.
Leading the gains were also property developers, shrugging off a downgrade of the sector by Moody's on Wednesday to negative from stable.
Reporting by Grace Li; Editing by Jacqueline Wong