HONG KONG — Thousands of protesters and riot police officers swarmed some of Hong Kong’s busiest neighborhoods on Sunday, cutting off traffic and freezing most retail activity in the city’s largest street mobilization in months.
But when the police blocked their route, deploying tear gas and water cannons, protesters splintered into clusters of dozens or sometimes hundreds that dispersed and reassembled repeatedly over the course of several hours.
“Hong Kong independence is the only way out,” protesters chanted as they poured onto a busy thoroughfare in the Causeway Bay shopping area. They sang songs and hoisted signs as they pressed forward, ignoring the warnings of dozens of police officers in riot gear to disperse.
The demonstration was the biggest in the territory in the several months since the coronavirus epidemic and rules on social distancing have kept many antigovernment protesters at home.
Tam Tak-chi, an activist from People’s Power, a pro-democracy group, held what he described as an open-air public health lecture at a street stall, distributing masks and social-distancing advice while also criticizing the city’s riot police officers and Beijing’s tightening grip.
“With the national security law, the people cannot be healthy,” Mr. Tam said. “Stand with Hong Kong. Fight for freedom.”
The police moved quickly to shut it down, and Mr. Tam was seen being taken away.
As the crowd thickened, trams sat immobilized on the rails, with passengers poking their phones out to film the activity. One protester jammed police cones under the tires of a minibus to prevent it from moving.
“I came out today to protest against the evil law China will impose on Hong Kong,” said Billy Lai, a 34-year-old social worker. “If everyone of us can do a little bit more, I hope we can bring changes to the society.”
Many tried to march west toward another district but were turned back when the police fired tear gas. The police said in a statement that its officers had to use the measure to disperse crowds who had blocked traffic and thrown umbrellas, water bottles and other objects at officers.
In Beijing, China’s foreign minister, Wang Yi, said that the protests that roiled Hong Kong for much of last year had posed a grave threat to national security, demonstrating that such legislation was long overdue.
“We must get it done without the slightest delay,” he said at a news briefing.
He sought to assuage concerns that the rules would be used as cover for squelching antigovernment dissent in the city, saying that the move targeted a “very narrow category” of acts that threaten national security.
“Instead of becoming unnecessarily worried, people should have more confidence in Hong Kong’s future,” he said.
The movement is also struggling to recover from the fallout of the coronavirus pandemic. Even before the local authorities enacted bans on large public gatherings, many Hong Kong residents chose to stay home and avoid crowds. Since January, attempts to revive the protests of last year had been sparsely attended and quickly stifled by the police.
Even as the threat of the virus has waned, some in the pro-democracy camp have said they prefer to express their discontent in potentially safer ways, such as boycotting businesses seen as sympathetic to Beijing.
The march on Sunday was planned before the national security announcement. It was originally intended to oppose a separate bill, in Hong Kong’s legislature, to criminalize disrespect of the Chinese national anthem. Antigovernment groups see that proposal as yet another indication of the mainland’s encroachment on Hong Kong.
“In the eyes of the Chinese Communist Party one-party dictatorship, advocacy for democracy is seen to be subversion,” said Lee Cheuk-yan, who led a small protest earlier Sunday in front of China’s Liaison Office, which represents the mainland government’s interests in the territory. “Of course this is a threat to the people of Hong Kong and the freedom we have enjoyed.”
The march Sunday was smaller than the huge rallies that filled Hong Kong streets last year to protest a bill that would have allowed extraditions to mainland China. The Hong Kong government eventually abandoned that law, but protests continued over issues like the use of force by the police and limits on democracy in Hong Kong.
This year, the police have taken a more assertive approach to the protests, trying to stop mass gatherings before they occur. They have also fined groups of protesters for violating social-distancing regulations put in place to limit the spread of the coronavirus.
The Hong Kong government previously tried to introduce security laws in 2003, but was stopped after a mass protest march. The city’s government has since avoided reintroducing such legislation.
Carrie Lam, Hong Kong’s Beijing-backed leader, said the local impasse made it necessary to have Beijing bring in such laws. But to many in Hong Kong, the intervention by the central government has dealt a heavy blow to the autonomy that the city was promised when it returned to China from British control in 1997.
Ezra Cheung and Elaine Yu contributed reporting.