BEIJING — Hong Kong faced new worries about its increasingly fragile freedoms on Tuesday after the Chinese government severely warned the city’s judiciary following a court decision to overturn a government ban on demonstrators wearing face masks.

In comments early Tuesday, the central government’s Hong Kong affairs office said the court judgment “blatantly challenged the authority” of China’s legislature and of Hong Kong Chief Executive Carrie Lam, and created “severe negative social and political impact.”

The remarks were the most stark and public instance of the Beijing government weighing in on a judicial decision in Hong Kong, which is guaranteed independent courts under the Basic Law, its mini-constitution.

The unusually pointed comments intensified one of the central grievances of Hong Kong protest movement — an encroachment of the mainland government in the semiautonomous territory’s affairs — and could exacerbate clashes after days of violent standoffs between riot police and pro-democracy demonstrators on university campuses. But they reflect the Chinese government’s diminishing patience for the unrest, as evidenced by an increasingly harsh line from Chinese officials and state media, some of which have urged police to use live ammunition against protesters.

Chinese leaders in recent days said it was the common responsibility of Hong Kong's judiciary, as well as the executive and legislature, to stop the unrest in the city. That triggered a rebuke from the city's bar association, which said that the judiciary must be allowed to operate free of interference.

On Monday, Hong Kong’s High Court nullified a ban on face masks at public gatherings, introduced by the city’s government last month using colonial-era emergency powers, saying it violated the Basic Law. Lam had pushed through the measure to help police identify anti-government demonstrators.

In comments released by state media, a spokesman for China's legislature, the National People's Congress, rejected the notion that a Hong Kong court had the power to rule on whether a law was constitutional.

"Only the National People's Congress Standing Committee can make that ruling and decision, any other body does not have the authority," said Zang Tiewei, the spokesman for the NPC's legal work committee.

Yang Guang, a spokesman for China's Hong Kong and Macao Affairs Office, said Beijing would "closely observe" how the mask ban proceeded through Hong Kong's courts. Judges are expected to hear further submissions Wednesday.

Beijing’s intervention fueled worries about the erosion of China’s “one country, two systems” formula under which Hong Kong is entitled to relative freedoms, including an independent judiciary, and a high degree of autonomy from the mainland until 2047 — half a century after its handover from British to Chinese rule.

Julian Ku, a constitutional law professor at Hofstra University who is familiar with Chinese law, said Chinese authorities have the right to offer an official interpretation on Hong Kong matters after local courts make a final decision.

While statements from officials in Beijing on Tuesday were not an official interpretation of the Basic Law, they appeared to be "a signal and a warning to the Hong Kong courts not to uphold the mask ban on appeal, else they force a legal confrontation with Beijing," Ku said. "This is an unusual way for the National People's Congress Standing Committee to intervene in Hong Kong affairs."

Stuart Hargreaves, associate professor of law at the Chinese University of Hong Kong, said Beijing's statement could be read in at least two ways: If China intended to deny Hong Kong courts the right to interpret the Basic Law in their decisions, that would be a "radical reduction" in judicial independence. But if the NPC was merely reiterating that its Standing Committee had the final right of interpretation of the Basic Law, that was already clear and long accepted by the courts.

In this Monday, Nov. 18, 2019, photo, protesters go down the steps at the front entrance of Hong Kong Polytechnic University in Hong Kong in attempt to flee.
Raf Wober / AP
In this Monday, Nov. 18, 2019, photo, protesters go down the steps at the front entrance of Hong Kong Polytechnic University in Hong Kong in attempt to flee.

"What makes Hong Kong attractive as a base for international finance is not only its access to the Chinese market but its robust and independent judicial system. If that independence is eroded over time, then eventually international investors will have to reevaluate whether Hong Kong remains a viable place to do business," Hargreaves said.

Months of anti-government dissent in Hong Kong, marked by intensifying violence, reached a head this week as riot police surrounded hundreds of front-line demonstrators barricaded inside Polytechnic University. Some managed to escape the police cordon in dramatic fashion late Monday, though others remained trapped.

Lam, Hong Kong's leader, told reporters on Tuesday that about 600 people had left the campus, and police estimated about 100 remained inside. She urged those holed up in the university to "put down the weapons and come out peacefully."

Hong Kong's new police chief, Chris Tang, said the purpose of the police operation was "only to maintain the law and public order."

Along with full democracy and other demands, protesters are calling for an independent investigation into police brutality, amid evidence of wrongdoing by the force during the months of clashes. Lam has resisted those calls, saying an existing police complaints watchdog with limited powers to call witnesses is sufficient to probe complaints.

U.S. Secretary of State Mike Pompeo tweeted Monday that the United States was "gravely concerned by deepening political unrest and violence" in Hong Kong. The Chinese government, Pompeo said, "must honor its promises to the Hong Kong people, who only want the freedoms & liberties they have been promised."

Liang and Crawshaw reported from Hong Kong.