SHANGHAI - China and Hong Kong stocks fell on Thursday, as worries over fresh COVID-19 outbreaks and mortgage-payment boycott overshadowed gains in tech shares on the conclusion of a cybersecurity probe into Didi Global with a big-ticket fine.

China's blue-chip CSI300 lost 1.1%, while the Shanghai Composite Index declined 1%. In Hong Kong, the benchmark Hang Seng was down 1.5%.

Investors were worried about the economic impact of new coronavirus outbreaks in China. The country reported 943 new coronavirus cases for July 20, including 200 symptomatic infections, compared with 1,012 new cases a day earlier.

Financial hub Shanghai said on Wednesday the current virus testing order would be extended for a month until end-August, requiring that residents take a nucleic acid test at least once a week.

Shenzhen vowed to "mobilise all resources" to curb fresh outbreaks, ordering strict implementation of testing and temperature checks, and lockdowns for COVID-affected buildings.

Chinese authorities continued to grapple with a mortgage boycott that has seen a growing number of home buyers refusing to repay loans on stalled real estate projects.

"Lingering caution persists for Chinese equities amid both virus and property sector risks," Yeap Jun Rong, a market strategist at IG Asia, wrote in a note.

China's CSI 300 Real Estate Index dropped 2.7%, down roughly 14% from its July 1 peak. Hong Kong-listed mainland developers slumped 4.7%.

Bucking the trend, tech shares rose, with China's STAR 50 Index rising 1.1%,

Hong Kong's Hang Seng Tech Index gained as much as 1.3%, after China's cybersecurity regulator announced a fine of $1.2 billion against Didi following a lengthy probe, removing uncertainty.

Shares of Chinese gaming companies also jumped, after China's commerce ministry announced government support to the sector, including plans to expand approvals for online games.

(Reporting by Shanghai Newsroom; Editing by Rashmi Aich)