New Delhi, Jan. 23 -- Two organizers of Hong Kong's long-running vigil commemorating the 1989 Tiananmen Square crackdown pleaded not guilty Thursday, while a third pleaded guilty before the trial brought under a national security law that has largely erased dissent in the city.

Chow Hang-tung, Lee Cheuk-yan and Albert Ho, former leaders of the Hong Kong Alliance in Support of Patriotic Democratic Movements of China, were charged with inciting subversion in September 2021 under the China-imposed national security law. Prosecutors allege "ending one-party rule," what the group had long called for, was against China's constitution.

Lee and Chow pleaded not guilty and a hearing for arguments over defense witnesses was scheduled to resume Fr...