Activists in Hong Kong held a demonstration outside Beijing's liaison office on Wednesday, accusing the central government of suppressing people who talk about the virus outbreak instead of taking steps to contain the epidemic.
Authorities in Wuhan, the epicentre of the outbreak, have been cracking down on activists and citizen journalists, including Fang Bin and Chen Qiushi, who reported on the situation before going missing.
Members of the Hong Kong Alliance in Support of Patriotic Democratic Movements of China and the League of Social Democrats marched to the liaison office to demand the release of those presumed to have been detained.
The protesters then tied their face masks to the gates of the compound as a symbolic gesture.
The chairman of the alliance, Lee Cheuk-yan, said the mainland activists were just telling the truth, and there has been no information on their whereabouts so far.
"Totally, 350 people have been charged with spreading rumours. This is absurd," said the former lawmaker.
"We now have a virus situation, people try to tell the truth and you charge them with spreading a rumour?" he asked.
Lee said that after such activists spoke out, the mainland authorities were forced to admit there had been an outbreak.
He told RTHK's Richard Pyne the Communist Party is more keen on suppression of free speech than fighting the coronavirus.