The US on Thursday denounced China as a “thuggish regime” after a state newspaper published the name and photo of a US diplomat talking to activists.
China has dismissed the attacks as “gangster logic”, and has repeatedly accused the US of interfering in Hong Kong.
The accusations come as activists gather at Hong Kong’s airport for three days of unauthorised protests.
Demonstrators dressed in black sat in the arrivals hall waving banners to raise awareness among international visitors.
Hong Kong has seen weeks of demonstrations, beginning with anger at an extradition bill and morphing into demands for greater freedoms.
The former British colony is part of China but enjoys more autonomy. It has a free press and judicial independence under the “one country, two systems” approach – freedoms activists fear are being increasingly eroded.
They have called for an independent inquiry into alleged police brutality during the protests, the complete withdrawal of the controversial extradition bill, and the resignation of Hong Kong’s leader Carrie Lam.