"Peaceful advocacy for human rights does not constitute a crime," the French and German foreign ministries said of Chow, recipient of the Franco-German Human Rights Award in 2023.

The 41-year-old was convicted alongside fellow activist Lee Cheuk-yan, 69.

"Alongside other activists..., Chow Hang-tung worked tirelessly to promote human rights and democracy in China, in particular" in Hong Kong, they said in a joint statement.

"We call for her immediate release and urge the authorities in Beijing and Hong Kong to respect all civil rights and freedoms."

Lee and Chow were charged in 2021 and have been behind bars since, under a Beijing-imposed national security law.

The activists face a maximum penalty of 10 years in jail. They are to be sentenced at a later date.

The EU warned the conviction "confirms the continuing deterioration of the freedoms of expression and assembly and a further shrinking of the space for independent civil society in Hong Kong."

A statement by the bloc's foreign affairs spokesperson Anitta Hipper said the "politically motivated prosecution... undermines confidence in the rule of law" in Hong Kong.

It urged authorities to "maintain space for an independent civil society, ensure freedom of expression and the right to peaceful assembly as guaranteed by the Basic Law," Hong Kong's mini-constitution which has governed the former British colony since it was handed over to China.