By Eustance Huang, CNBC • Updated on July 27, 2021 at 11:16 pm Jiang Ning | VCG | Getty Images The CSI 300 which tracks the biggest mainland China stocks, along with Hong Kong's Hang Seng index, are currently among the worst-performing in Asia-Pacific. Separately, the MSCI Emerging Markets index has also tumbled into negative territory for the year. Chinese internet giants like Tencent, Alibaba and Meituan are among the top 5 constituents of the index, as of Jun 30. The declines come as Chinese regulators continue to step up their oversight in sectors spanning from technology to ...