HONG KONG — Thousands of masked protesters marched through two Hong Kong shopping districts on Sunday, defying a new ban on face coverings at public gatherings and raising the prospect of more violent showdowns between protesters and the police.
The marches, in the pouring rain, were the first significant public gatherings since the ban took effect early on Saturday. Outside the shuttered malls and stores of the Causeway Bay district, the large crowds of protesters, many wearing blue, gray or black masks, chanted “Hong Kongers, resist!” Another march took place across the harbor in the Tsim Sha Tsui neighborhood.
In announcing a ban on the protesters’ ubiquitous face masks on Friday, Hong Kong’s deeply unpopular leader invoked a colonial-era emergency powers law that allows for new regulations when the territory faces “a state of serious danger.”
The announcement unleashed violent protests across the city on Friday. Hong Kong was quieter on Saturday, as a shutdown of the entire subway system brought the city to a near standstill, but masked protesters openly flouted the ban at scattered gatherings.
The large marches and the widespread defiance of the emergency proclamation on Sunday were both a symbol of the staying power of the nearly four-month-old protest movement and a potential test of local officials’ resolve to stop the demonstrators’ momentum.
“Maybe they’re trying a new model of dealing with the Hong Kong situation — of turning it into a de facto emergency state,” said Gary Fong, a lecturer at Hong Kong Community College who studies policing strategies.
From a tactical perspective, he added, the face mask ban will not help police officers much, mostly because the rule carries a maximum jail term of only one year — a tenth of what protesters already faced whenever they joined any of the many unauthorized marches.
And when it comes to punishing protesters, he added, police officers still face an obvious challenge: “You have to catch them.”
More broadly, the marches posed another test to a local economy that is under heavy strain from the protests, as well as testing the patience of China’s Communist Party leaders, who have watched the Hong Kong protests warily for months and warned that using force against them is an option.
The protests began four months ago in opposition to a now-abandoned bill that would have allowed the extradition of criminal suspects to the mainland. There have since been dozens of violent street clashes between demonstrators and police officers, and they have steadily grown more combative and dangerous.
On Tuesday, a protester was shot by the police for the first time since the demonstrations began, and another was shot on Friday, though the police did not claim responsibility. Both protesters were teenagers.
The Hong Kong authorities are “using the police force to solve political problems” and stifling public opinion in a way that leaves little daylight between Hong Kong and mainland China, said Ken Chan, a 21-year-old university student who joined the rally in Causeway Bay.
When the protests began in June, “our original motivation was based on the fear that Hong Kong will become like the mainland,” said Mr. Chan, who wore a gray mask to the rally. “So when they impose this ban, it will only set people off further.”
The face mask ban applies to public gatherings of more than a few dozen people and is punishable by a fine in addition to the one year in jail. But enforcing the ban is likely to prove difficult because face masks are a common feature among protesters, who use them to guard against tear gas and protect their identities.
The ban draws on the so-called Emergency Regulations Ordinance, a colonial-era law that offers Hong Kong’s leader extensive legal authority to bypass the local legislature. It was last used during deadly pro-Communist riots in 1967 that targeted the British government that administered the city.
Hong Kong’s leader, Carrie Lam, delayed invoking the law for weeks, out of concern that it would hurt efforts to persuade residents, tourists and international businesses that the city is still a safe place. She appears to think the ban’s potential upside — dissuading moderate Hong Kongers from joining demonstrations — is worth the damage it would inflict upon her reputation.
But Hong Kongers are also deeply sensitive to efforts to erode the civil liberties that have long differentiated their city from the rest of China and helped make it an attractive destination for international bankers and investors. And many here see the ban — like the contentious extradition legislation that triggered the protests — as something that could fundamentally change the city’s identity.
Mr. Chan, the protester in Causeway Bay, said he did not think the mask ban would significantly depress the turnout for rallies or marches in Hong Kong because protesters were already facing rioting charges that carry jail terms of up to 10 years just for showing up at rallies that the police deem unauthorized.
“But undoubtedly, those who are more fearful might not dare,” he added.
The ban could still inflame hard-core protesters who have increasingly resorted to violence and widespread vandalism as a way of pressing the movement’s demands for government accountability and democratic reforms.
And it has already prompted stiff opposition from Mrs. Lam’s opponents in Hong Kong’s legislature.
On Saturday, 24 members of the city’s pro-democracy legislative minority asked a Hong Kong court to put the mask ban on hold. They accused Mrs. Lam of overstepping her legal authority under the Basic Law, the mini-constitution that has governed Hong Kong since Britain handed it back to Chinese control in 1997.
“Today is a battle between totalitarianism and the rule of law,” one of the lawmakers, Dennis Kwok, told reporters on Sunday morning. “So the government can implement any law they want — is that the way it is now? Or is Hong Kong still a society under the rule of law?”
Mrs. Lam has called Mr. Kwok’s argument “groundless.” And on Sunday — just before the Causeway Bay rally began — the city’s High Court threw out the request for an injunction against the ban.
Ezra Cheung, Katherine Li and Edward Wong contributed reporting.