The Hong Kong Public Opinion Research Institute (HKPORI) has been targeted by authorities multiple times since Beijing imposed a sweeping national security law on Hong Kong in 2020 to quell dissent.

The pollster said in a statement it will "suspend all its self-funded research activities indefinitely, including its regular tracking surveys conducted since 1992, and all feature studies recently introduced".

"HKPORI will undergo a transformation or even close down."

Police in December placed a HK$1 million ($128,000) bounty on the group's former deputy CEO, Chung Kim-wah, accusing him of advocating separatism and calling for sanctions against China.

Chung, who is based in Britain, said he has severed ties with his former employer.

In Hong Kong, national security police have brought in CEO Robert Chung and multiple HKPORI staffers for questioning over the past month, without arresting them.

The CEO said Thursday that he "welcomes interested parties to take over the institute".

Hong Kong's security chief earlier told AFP that the police action had "absolutely nothing to do with the results of (the group's polls)".

First established as a university programme in 1991, the institute started polling in the final years of British colonial rule before the city was handed over to China in 1997.

One of the city's most closely watched polls would ask residents if they identified as "Hongkongers", "Chinese", or some combination of the two.

Hong Kong police in 2020 and 2021 raided the institute's office after it helped pro-democracy activists organise an informal primary election.

In 2023, the group stopped publishing polling data for topics such as the 1989 Tiananmen crackdown and Taiwan's independence -- issues deemed taboo by Beijing.

The pollster on Thursday said it has "always been law-abiding, but in the current environment, it has to pause its promotion of scientific polling".