Hong Kong police on Thursday announced that a protest scheduled for Sunday will be banned on the grounds that it might endanger “public safety.”

The ban was issued just two hours before protest organizers planned to hold a press conference to discuss the weekend march. Organizers said they would appeal the decision.

The march was organized by the Civil Human Rights Front (CHRF), which has produced some of the largest recent protest events. The CHRF requested a permit (technically referred to as a “letter of no objection” in Hong Kong) for a march on Sunday from Causeway Bay to Charter Road in the central part of the city.

The theme of the march was “Five Demands, Not One Less,” a slogan that became popular after the first of the five key demands made by the protest movement was belatedly granted by Chief Executive Carrie Lam, who permanently withdrew a controversial bill that would have made extradition to China easier.

The police objected to the plan to protect “public safety, public order,” and the “rights and freedoms of others.” Supplying a list of 25 events over the past three months that involved violent confrontations between protesters and police, the police argued that mass protests of the sort planned by the CHRF posed an unacceptable risk to vital facilities.

“The public meeting and march that you proposed is very close to high-risk facilities, including Causeway Bay MTR station, Wan Chai MTR station, Wan Chai Police Headquarters, Admiralty MTR station, Central Government Offices, Central MTR station, Government House and the Court of Final Appeal,” the police told the CHRF.

“MTR” is Hong Kong’s metro rail system. MTR stations have become common venues for protest actions, in part because of lingering anger over violence directed at protesters by police and gang thugs widely suspected to be working for the Chinese government.

Activists have accused the rail service of caving in to pressure from Beijing by closing stations and canceling services to make it harder for demonstrators to get around the city, and for refusing to release security camera footage they believe will show the police initiating much of the violence blamed on protesters.

The police letter went on to speculate that groups of violent protesters could break away from the main march and commit acts of vandalism on these high-risk targets — a line of reasoning that could be invoked to ban virtually all large demonstrations in Hong Kong going forward.

In a separate announcement, MTR officials said they would cancel overnight train service for the Mid-Autumn Festival on Saturday, citing the risk of vandalism to its stations.

In previous years, the MTR has furnished trains into the wee hours for participants in the popular festival, which includes many family reunions. Overnight train service is also routinely provided for Christmas Eve, New Year’s Eve, and the Chinese holiday of Lunar New Year.

Protest organizers said they would hold another “stress test” at the Hong Kong airport this weekend — a vague invitation for people to hang out around the airport in huge numbers, because organized protest actions at the facility have been made illegal — and would demonstrate outside the British consulate to remind China of the agreement it signed in 1984 to preserve Hong Kong’s autonomy after it took ownership back from the U.K. in 1997.

Protesters said they would form human chains carrying paper lanterns during the Mid-Autumn Festival, which prominently features paper lanterns. Sit-ins are planned for shopping malls and major tourist attractions like Victoria Peak and Lion Rock.

Another traditional aspect of the Mid-Autumn Festival is the mooncake, a small muffin filled with lotus seed paste. At least one popular bakery is selling mooncakes with protest slogans baked into the top, ranging from the widespread advice for Hong Kongers to “add oil” (i.e. “step on the gas” and demand their freedoms with even more vigor) to sarcastic quotations of profane insults that have been directed at protesters by angry police officers. The Wah Yee Tang bakery is reportedly having difficulty keeping up with the immense demand for protest mooncakes.

Another mooncake supplier, Taipan Bread and Cake, came under attack by Chinese Communist state media because its director wrote Facebook posts supporting the protest movement. Taipan Bread and Cake was soon delisted from Chinese online shopping services, its cakes were removed from store shelves, and shipments of its products were destroyed by Chinese importers.