China's Assistant Minister of Foreign Affairs Zhang Jun says China will not allow the G20 to discuss the Hong Kong issue at its upcoming summit.
Millions of people have demonstrated on the streets of Hong Kong this month to rally against a bill that would allow people to be extradited to the mainland to face trial in courts controlled by the Communist Party.
It triggered the most violent protests in decades when police fired rubber bullets and tear gas to disperse the crowds. Beijing's squeeze also sparked pro-democracy protests in 2014 that paralysed parts of the city for 79 days.
Hong Kong matters are an internal Chinese affair, Zhang said at a briefing in Beijing on Monday, and will not be discussed in Osaka on June 28-29.
"Hong Kong is China's special administrative region. Hong Kong matters are purely an internal affair due China. No foreign country has a right to interfere," Zhang told reporters.
"No matter at what venue, using any method, we will not permit any country or person to interfere in China's internal affairs."
Chinese President Xi Jinping and US President Donald Trump will also meet in Osaka amid heightened trade tensions.
Australian Associated Press