HONG KONG--Hong Kong police searched the office of an independent political pollster on Friday, 10 days after Beijing imposed sweeping national security legislation that has sent a chill across the former British colony.

The raid came ahead of weekend primary elections for which pollster Robert Chung's Hong Kong Public Opinion Research Institute (HKPORI) is a co-organizer.

The primaries for Hong Kong's pro-democracy camp aim to select candidates who will stand the best chance of achieving a 35-plus majority in Legislative Council polls in September.

Chung told Reuters authorities arrived at his office and he "negotiated" with police to try to understand the basis for their search warrant. He said police copied some information from computers.

Police confirmed to Reuters they had searched his office.

"The police received a report from the public that the computer system of a polling organization was suspected of being hacked and some personal information of the public was leaked," they said in a statement.

"The investigation is still ongoing and no one has been arrested."

Chung told a news conference early Saturday he was worried the information police obtained could be used in other investigations but would do his best to protect his sources. He did not describe the nature of the data taken.

"We obtained an oral promise that they wouldn’t use it for other investigations," Chung said.

Last year, Chung, who has repeatedly been criticized by pro-Beijing forces who question the accuracy of his polls, broke away from a polling operation he oversaw at the University of Hong Kong to set up his independent HKPORI.

Former Hong Kong democracy lawmaker Au Nok-hin said he believed the raid was related to the primary elections and were aimed at stoking fear in the community.

HKPORI conducted three public opinion polls for Reuters on how residents of the city saw the sometimes violent pro-democracy protest movement that began in 2019. The surveys were conducted in December, March and June.

In the most recent poll, almost half of Hong Kong residents polled said they were "very much opposed" to Beijing’s move to implement national security legislation in the city that returned to Chinese rule in 1997 with a guarantee of wide-ranging autonomy.

The poll also showed support for the protest movement fading even as most people continued to voice support for its key demands, including universal suffrage and the resignation of Hong Kong leader Carrie Lam.

One question in the survey asked residents if they supported independence for Hong Kong, a political call that is a red line for Communist Party rulers in Beijing and has already become a target under the new security law.

Of those surveyed, 21% said they supported an independent Hong Kong, about unchanged from March. Opposition to the idea was at 60%.

Beijing imposed the national security legislation just before midnight on June 30, making crimes of secession, subversion, terrorism and collusion with foreign forces punishable with up to life in prison.

The Hong Kong and Chinese government officials have said the law is vital to plug gaping holes in national security defenses exposed by the months of anti-government and anti-China unrest.

They have said action was vital given the city’s failure to pass such laws by itself as required under its mini-constitution, known as the Basic Law.

The primary elections come ahead of Legislative Council polls on Sept. 6, when the pro-democracy camp hopes to secure a 35-plus majority in the legislature, giving them power to block government proposals and potentially paralyze the administration.

Pro-Beijing lawmakers have said that the democrats' aim to disrupt the administration could lead to a constitutional crisis.

Secretary for Constitutional Affairs Erick Tsang warned this week that the primary election could violate the new security law, drawing a swift rebuke from the democracy camp.