Beijing has told foreign consulates in Hong Kong to hand over the personal details of all locally hired staff.
Local media reported that a letter from the city arm of China's Foreign Ministry asked for the data to be submitted by 18 October.
The requirements apply to all foreign missions' local employees, including permanent residents and non-permanent residents in the financial hub.
The move is in line with "international practice", the foreign ministry said.
It would also bring rules in Hong Kong in line with those on the mainland.
"The Chinese side has been managing the affairs of foreign consular offices in Hong Kong in accordance with the law and from a practical point of view," the ministry said on Wednesday, in response to queries seeking confirmation of the move.
Hong Kong is part of China, but has had some autonomy since the end of British rule in 1997.
But following months of major demonstrations in 2019, Beijing tightened its control over the city by imposing a strict national security law outlawing many forms of dissent. Just this week, Hong Kong police arrested a 46-year-old office clerk for allegedly posting seditious content online.
The latest requirement from Beijing is believed to be the first time such a policy is being implemented in the territory. Chinese employees of foreign embassies and consulates on the mainland are already required to hand over personal details of locally hired staff.
The information to be submitted to Chinese authorities includes the member of staff's job titles, residential addresses, and identity card numbers.
Consulates have also been asked to report new hires' personal details within 15 days once they start work, according to local media.
The letter stated that the collected data could be passed on to other authorities "for exercising their function in relation to managing the presence of the staff locally engaged", the South China Morning Post reported.
The Commissioner's Office of China's Foreign Ministry in Hong Kong has not specified the purpose of the new rules.
They were announced as the UK released on Wednesday its latest six-monthly report on Hong Kong, wherein it noted that freedoms there are under "significant pressure".
The report said authorities in Hong Kong have been using the national security law "beyond genuine national security concerns". It mentioned the crackdown on the protest anthem Glory to Hong Kong and the detention of British citizen Jimmy Lai, who is on trial for subversion.
The UK's six-monthly reports aim to monitor China's commitment under the 1997 handover to give Hong Kong some autonomy for 50 years or until 2047.
Hong Kong's foreign ministry called the UK's January to June 2023 report "fallacious" and asked it to "immediately stop interfering" in "purely China's internal affairs".