Hong Kong Exchanges and Clearing Limited has rolled out a Volatility Control Mechanism to protect market integrity. The new measure will impose a five-minute trading limitation if a stock's price moves over 10 percent on either direction.

Only 81 Hong Kong stocks, including HSBC Holdings and Tencent, will be subject to this new system. Each stock has only two chances to trigger the mechanism in each of the two trading sessions. This will prevent extreme price volatility which might arise from major trading errors or other unusual incidents.