China 'will not sit by' if HK crisis worsens: Chinese envoy

China will not "sit by and watch" and is ready to "quell the unrest swiftly" if the crisis in Hong Kong becomes "uncontrollable", China's ambassador to London Liu Xiaoming said on Thursday.

"If the situation deteriorates further into unrest uncontrollable by the SAR (Special Administrative Region) government, then the central government will not sit by and watch. We have enough solutions and enough power to quell the unrest swiftly," he said.