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 fell 0.3% to 4,932.71 points at the end of the morning session, while the Shanghai Composite Index lost 0.4% to 3,629.61 points.

The Hang Seng index added 0.1% to 23,223.76 points. The Hong Kong China Enterprises Index 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.

** New energy vehicle giant BYD has had to cut production at its plant in Xian, the South China Morning Post reported.

** BYD's Shenzhen-listed shares slumped 3.7%, while its Hong Kong stocks dropped 1.5%.

** The new energy subindex tumbled 3.5%, with new energy vehicles and the photovoltaic industry down 4.1% and 2.8%, respectively. Chinese battery giant CATL 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 and machinery stocks 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 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 edged down 0.3%, while mainland developers listed in Hong Kong closed 0.6% lower.

(Reporting by Shanghai Newsroom; Editing by Devika Syamnath)