On colonial-era charges of "seditious publication," Hong Kong police arrested six current and past employees of the local news service Stand News on Wednesday.
The raid also casts doubt on the former British colony's freedom of expression and media, which returned to Chinese sovereignty in 1997 on the assurance that a broad range of individual rights would be preserved.
Authorities said about 200 officers in both uniform and plainclothes were sent to the publication's office in the Kwun Tong district. Searches of the journalists' homes are still being conducted, police said.
Former chief editor Chung Pui-kuen, barrister and former pro-democracy lawmaker Margaret Ng, and pop singer Denise Ho, as well as acting chief editor Patrick Lam, were among the six persons arrested, according to Hong Kong broadcaster TVB.
Under the comprehensive national security law imposed on the city by China in June last year, sedition is not a crime.
However, recent court rulings have permitted authorities to use the new legislation's provisions to execute previously underutilized colonial-era statutes, such as the Crime Ordinance, which encompasses sedition.
After Apple Daily, which shuttered in June after authorities froze its assets under a national security law enacted by China to quell opposition, Stand News is the second Hong Kong media outlet targeted by national security officers.
According to police, they arrested three men and three women ranging in age from 34 to 73.
The Stand News bureau office was partially cordoned off by police, a Reuters reporter at the scene said.
Four police vans stood in front of the publication's office, while officers wandered about the lobby.
On the 14th floor, a police media liaison officer stated that entry to the office would be denied because of an "ongoing operation." The officer declined to provide additional information.
One of those held was Ronson Chan, the publication's deputy assignment editor and the chairman of the Hong Kong Journalists Association, according to Stand News.
The news site published a video of police officers entering Chan's home and displaying their court warrant. Chan was apparently contacted by authorities to aid with their investigation but was not apprehended.
The raids take place 18 months after the National Security Law, which criminalizes secession, subversion, terrorism, and coordination with foreign forces, was established.
As a result, political opposition has been largely repressed, pro-democracy media forced to close or self-censor, and political and advocacy organizations abolished. Thousands of residents have fled to neighboring countries as a result of the clampdown.
