A women’s rights group has abruptly called off what would have been the first authorised rally in Hong Kong in three years, although the reason for the cancellation remained unclear.

The Hong Kong Women Workers’ Association planned to hold the demonstration on Sunday, ahead of International Women’s Day on Wednesday, but informed police on Saturday it had called off the event.

The group had obtained a letter of no objection from police after seeking permission to hold the rally. While the association expressed “regret” over the cancellation and did not offer to explain its decision, a police superintendent said violent groups had expressed an intention to take part.

“Although police do not want anyone to defy the law, police still observe many people, including violent gangs, who have expressed their eagerness to answer the call [of the organiser],” said Dennis Cheng Wai-kin, acting senior superintendent of the Hong Kong Island regional headquarters.

Dennis Cheng, acting senior superintendent of the Hong Kong Island regional headquarters.

Cheng warned that anyone who assembled at the relevant locations could be prosecuted for taking part in an unauthorised assembly.

“In the interests of national security, public safety, public order and other concerns, police have the duty to adopt various appropriate measures to prevent any unlawful activities,” he said. “Police will deploy adequate manpower at relevant locations on the day and take resolute enforcement action.”

Cheng added the force respected the organiser’s decision , saying the group had “struck a balance of different factors”. But he would not comment further on the matter.

Protests to call attention to demands ranging from workers’ rights to greater democracy were regularly held in Hong Kong in the decades since the handover from British to Chinese rule in 1997.

After often-violent anti-government protests erupted in 2019, authorities imposed a ban on wearing masks at demonstrations. The following year, the first cases of Covid-19 emerged in the city and the government limited the number of people allowed to gather in public, in addition to imposing a requirement that residents wear masks to protect themselves against the virus. The restrictions on social gatherings were abandoned in December, while on Wednesday, the mask mandate came to end.

On Wednesday Chief Executive John Lee said the mask ban and the Covid-19 mask mandate were “two different homes.”

“The mask mandate was for public health matters. As for the mask ban, we will review it at a suitable time. At this moment, we will not handle it,” he said.

Ronny Tong Ka-wah, a barrister by training and one of Lee’s top advisers, on Friday said anyone who wore a mask during a protest should consider “the level of risk of prosecution” for the act.

The ban applies to regulated assemblies, public meetings and public processions.

Those who fail to comply with the rule are liable to a maximum penalty of a HK$25,000 (US$3,185) fine and one year in jail.

Earlier this year, the Tin Wan Kai-Fong Federal Association and the Kowloon City District Recreation and Sports Council succeeded in applying for police approval to hold events to celebrate the birthday of the goddess of mercy Guanyin on Sunday.