HONG KONG — The Hong Kong police arrested dozens of elected pro-democracy officials and activists early Wednesday on suspicion of undermining a new national security law after they tried to organize an informal primary election last year for the city’s legislature.
The mass arrests marked the largest roundup yet under the security law, which the central Chinese government imposed on Hong Kong in June to quash dissent after months of fierce anti-Beijing protests. The move on Wednesday suggested that the authorities were casting a wide net for anyone who had played a prominent role in opposing the government.
The Hong Kong police did not immediately identify those arrested, and said an exact count of those detained was not available. But some local news outlets reported that up to 50 people had been arrested.
The wide-ranging nature of the arrests — which included figures who had called for aggressive confrontation with the authorities and those who had supported more moderate tactics — underscored government officials’ efforts to weaken any meaningful opposition in the city’s political institutions. Along with detaining activists, the authorities arrested at least 10 former Legislative Council members and a number of district councilors, a hyperlocal elected position dominated by pro-democracy figures.
Pro-democracy forces have increasingly faced pressure over the past year. Before the latest roundup, the police previously arrested dozens of people under the national security law, including Jimmy Lai, the media mogul and founder of Apple Daily, a pro-democracy newspaper.
The Hong Kong government had disqualified several pro-democracy candidates from running in the election for the Legislative Council. In November, the government disqualified four pro-democracy incumbents who it said had supported or had been inadequately critical of U.S. sanctions on the city. The remaining opposition members resigned in protest.
“This is a total sweep of all opposition leaders,” said Victoria Hui, an associate professor of political science at the University of Notre Dame who studies Hong Kong. If running for office and trying to win election are considered subversion, she added, then the security law “is aimed at the total subjugation of Hong Kong people.”
“There should be no expectation of elections in any sense that we know it if and when elections are held in the future,” Ms. Hui said.
The unofficial primary, which was held in July, was organized by the pro-democracy camp in an effort to pare down the number of candidates in the September election for Hong Kong’s Legislative Council. Dozens of candidates had expressed interest in running despite a voting system that gives significant advantages to establishment candidates. The pro-democracy camp, which had a long shot of winning a majority, had wanted to try to ride the momentum created by the landslide defeat of establishment candidates in the 2019 district council elections.
If they had managed to win, many of the opposition candidates had said they planned to use that majority to block the government’s agenda, including vetoing the annual budget. If the budget is vetoed twice, the chief executive would be forced under Hong Kong law to step down.
Government officials had warned that such a plan could be considered subversion under the national security law. The September election never took place. The Hong Kong government postponed it in late July by one year, citing coronavirus concerns. Many democracy supporters accused officials of trying to prevent an embarrassing loss for the pro-Beijing camp.
More than 600,000 Hong Kongers voted in the July primary election, largely selecting newer candidates who favored a more aggressive approach toward the government, rather than more familiar moderate faces. Some of the activists arrested on Wednesday were among the more outspoken winners. But the police also arrested candidates who had lost their primary races and were less directly involved with the mass protests.
In a Facebook Live video streamed by Ng Kin Wai, a district councilor, as the police arrived at his door on Wednesday, an officer could be heard saying that he was arresting Mr. Ng on suspicion of “subversion of state power.” The officer says he has “reason to believe” that Mr. Ng had participated in the primary in order to win office and ultimately “force Chief Executive Carrie Lam to resign.”
Au Nok-hin, a former Legislative Council member who helped organize the primary, was also arrested on Wednesday. He had stepped down from his organizing role after the government warned the effort could amount to subversion.
The Twitter account of Joshua Wong, the former student leader who is one of the most prominent faces of the Hong Kong protests, said that the police had also raided Mr. Wong’s home on Wednesday morning because he had participated in the primary.
Mr. Wong is serving more than a year in jail for his role in a 2019 protest, a charge not linked to the national security law. Convictions under the security law can lead to significantly longer sentences.
Also on Wednesday, police officers delivered a court order to Stand News, a news organization seen as supportive of the protests, requesting documents. They raided the offices of Apple Daily last year.
Human rights groups condemned the mass arrests. Maya Wang, senior China researcher at Human Rights Watch, said the authorities had removed “the remaining veneer of democracy in the city.”
“Repression generates resistance,” Ms. Wang said in a statement, adding that “millions of Hong Kong people will persist in their struggle for their right to vote and run for office in a democratically elected government.”
Nathan Law, a prominent Hong Kong activist who fled to London last year, called on the European Union to impose sanctions on Hong Kong and Chinese officials involved in the arrests.
Tiffany May contributed reporting.