SHANGHAI, Dec 24 (Reuters) - China stocks fell on Friday as new energy shares tumbled, while a local outbreak of COVID-19 weighed on some business operations and investor sentiment. The Hong Kong stock market closed higher at midday, ahead of a Christmas holiday. The CSI300 index (.CSI300) fell 0.3% to 4,932.71 points at the end of the morning session, while the Shanghai Composite Index (.SSEC) lost 0.4% to 3,629.61 points. The Hang Seng index (.HSI) added 0.1% to 23,223.76 points. The Hong Kong China Enterprises Index (.HSCE) was unchanged at 8,201.95. ** For the week, the CSI300 index slipped 0.4%, while the Hang Seng index inched up 0.1%. ** Rising COVID-19 infections in China"s city of Xian have spurred a lockdown of its 13 million residents, and several companies have said their operations have been affected. read more ** New energy vehicle giant BYD (002594.SZ) has had to cut production at its plant in Xian, the South China Morning Post reported. ** BYD"s Shenzhen-listed shares (002594.SZ) slumped 3.7%, while its Hong Kong stocks dropped 1.5%. ** The new energy subindex (.CSI399808) tumbled 3.5%, with new energy vehicles (.CSI399976) and the photovoltaic industry (.CSI931151) down 4.1% and 2.8%, respectively. Chinese battery giant CATL (300750.SZ) plunged 7.1%. ** New energy shares have surged this year amid China"s green push, and some investors are taking profits, analysts said. ** Non-ferrous metals (.CSI000811) and machinery stocks (.CSI000812) dropped more than 2.9% each. ** Hong Kong shares were trading sideways in thin-volume trade ahead of a Christmas holiday. ** Gambling stocks listed in Hong Kong (.CSICESG10) surged 3.8% after Macau"s Gaming Inspection and Coordination Bureau published a report summarizing opinions on proposed gaming law revisions. ** The Hang Seng Tech Index (.HSTECH) edged down 0.3%, while mainland developers listed in Hong Kong (.HSMPI) closed 0.6% lower.