(Bloomberg) — Hong Kong braced for another tense National Day, as authorities threatened to arrest anyone who turned out to protest a Beijing-backed crackdown on dissent in the Asian financial center.

The Chinese government warned that those who defy a protest ban on the anniversary of the founding of the People’s Republic in 1949 on Thursday risked running afoul of a powerful new national security law. Some 6,000 riot police were expected to be deployed to prevent demonstrators from taking to the streets or interrupting events, including a flag-raising ceremony attended by Chief Executive Carrie Lam.

Some activists urged supporters in online forums to turn out anyway, with one group calling for a 2 p.m. march in the Mong Kok shopping district and others calling for people to wear black and carry glow sticks for “non-assemblies” in the evening. Police announced the arrests of five activists this week on allegations that they incited people to attend unlawful gatherings.

Earlier this week, an appeals panel upheld a police ban on a protest sought by the Civil Human Rights Front, which last year organized largely peaceful marches that drew more than a million people. Police cited the threat of violence and coronavirus measures that currently bar gatherings larger than four people.

“We have been fighting for over a year,” a Hong Kong University of Science & Technology student named Tse said. “If people do turn up, they will be there to express their concerns or express their non-compliance to the national security law. Many young people don’t like how the government is treating its people.”

The plight of a dozen Hong Kong activists held on the mainland since attempting to flee to Taiwan by boat in August was among the concerns protesters wanted to highlight. China has approved the arrests of 12 people on allegations of organizing or participating in an illegal border crossing, according to district prosecutors from the mainland city of Shenzhen in a statement late Wednesday. While prosecutors didn’t identify the suspects as being from Hong Kong, the surnames of four of them matched those of the activists.

Secretary of State Michael Pompeo has said the U.S. was “deeply concerned” about the activists, who are ages 16 to 33 and include one person facing possible prosecution under the security law.

The Oct. 1 holiday was the latest test of Hong Kong’s efforts to contain unrest that helped drive the former British colony into recession last year even before the coronavirus pandemic. Massive protests undercut President Xi Jinping’s efforts to convey national strength on the 70th anniversary of Communist Party rule last year, as demonstrators clashed with police and one protester was shot by a riot officer.

Xi took unprecedented action to impose the security law without local debate in June, giving authorities the power to jail for life those convicted of crimes including subversion and collusion with foreign powers. The Group of Seven nations has denounced the move as a breach of China’s promise to preserve the financial hub’s autonomy, and the U.S. leveled sanctions against Lam and other top officials.

The Beijing-backed government has rejected the criticism, so far arresting 23 activists under the law including media tycoon Jimmy Lai. On Tuesday, China’s top agency in the special administrative region warned that measure could used against those who protest on the national holiday.

“We solemnly warn that the sword of Hong Kong’s national security law is hanging high, and we will not allow those who disturb Hong Kong to act recklessly,” the Liaison Office said. “We firmly support the SAR government and the police in decisively enforcing the law to ensure a happy and peaceful festival for the general public.”

The Hong Kong Police Force have ramped arrests since protests erupted last year against Lam’s proposal to allow extraditions to the mainland. After making some 6,600 arrests last year, police have arrested another 3,400 this year, even though the coronavirus and national security law have resulted in far fewer protests.

Those who attend an unauthorized protest are liable for crimes ranging from inciting an unlawful assembly to rioting, a colonial-era charge that carries a sentence of as long as 10 years in prison. Still, thousands of Hong Kong residents defied warnings to return to the streets on Sept. 6, in a show of anger over the government’s decision to postpone the election by a year over the pandemic. Hundreds were arrested.

Support for several of the protest movement’s goals increased over two months, according to a Reuters/Hong Kong Opinion Research Institute poll released in August. The share in favor of Lam’s resignation rose to 58% and direct elections for her replacement were backed by 63%. Some 51% said they “very much oppose” the national security law.

Nick Or, an assistant professor of public policy at the City University of Hong Kong, said the government would be better off trying to resolve the underlying disputes if it wanted to see fewer protests.

“The potential social unrest that may happen on Oct. 1 is a manifestation of the fact that the political system in Hong Kong fails to set up an institution to address the demands and grievances in society,” Or said.

©2020 Bloomberg L.P.