China on Wednesday opened a new office for its intelligence agents to operate openly in Hong Kong for the first time under a tough new security law, transforming a hotel into the force's headquarters.

The new base is a hotel overlooking the city's Victoria Park, a location that has hosted pro-democracy protests for years, including an annual vigil each June marking Beijing's deadly Tiananmen crackdown.

Security barriers ahead of the inaugural ceremony
Security barriers were thrown up around the hotel overnight ahead of the inauguration ceremony. Photo: AFP / Anthony WALLACE

A plaque bearing the security agency's name was unveiled early Wednesday in front of Hong Kong government and police officials, an AFP reporter on the scene said.

Police blocked roads around the hotel and surrounded it with water-filled barriers.

A Chinese flag was unfurled on a pole erected outside the building while a plaque bearing the emblem of the People's Republic of China went up overnight.

China's new HK security agency headquarters
A sign saying hotel is now undergoing minor work is stuck to covered-up windows at the Metro Park hotel, which is being retrofitted and turned into a new office for Chinese security agents to operate openly in Hong Kong. Photo: AFP / ISAAC LAWRENCE

"The Office for Safeguarding National Security of the Central People's Government in the Hong Kong Special Administrative Region was inaugurated here on Wednesday morning," China's official Xinhua news agency said.

Beijing imposed a new security law on Hong Kong last week targeting acts of subversion, secession, terrorism and foreign collusion.

Hong Kong Security Law
Key points of China's newly imposed national security law for Hong Kong Photo: AFP / John SAEKI

The law is the most radical change in Hong Kong's freedoms and autonomy since Britain handed the city back to China in 1997.

Similar national security laws are used to crush dissent on the mainland and police in Hong Kong have already made arrests for people voicing certain political views now deemed illegal, such as advocating independence or autonomy.

Police speak to staff
Police speak to staff at the front door of the Metro Park hotel in Causeway Bay. Photo: AFP / ISAAC LAWRENCE

The content of the security law was kept secret until it was enacted last Tuesday, bypassing Hong Kong's legislature.

China has said it will have jurisdiction over the most serious cases, toppling the legal firewall that has existed between its party-controlled courts and Hong Kong's independent judiciary since the handover from Britain in 1997.

China's new HK security agency headquarters
China opens a new office for its security agents to operate openly in Hong Kong for the first time under a tough new law, transforming a hotel into the force's headquarters. Photo: AFPTV / Michael ZHANG

Among the many precedent-breaking provisions the law contains is authorisation for China's security apparatus to work openly inside Hong Kong, with powers to investigate and prosecute national security crimes.

Until then Hong Kong's own police and judiciary had complete jurisdiction over the semi-autonomous finance hub.

But China argues national security is the responsibility of the central government and says the laws are needed to restore stability after huge and often violent pro-democracy protests last year.

Not much is known about the new security office China has opened in Hong Kong beyond its top leadership.

On the authoritarian mainland, China's secret police are the speartip of a highly efficient and ruthless security apparatus that tolerates no dissent.

Last week Beijing appointed Zheng Yanxiong to head up the agency.

A party hardliner and a speaker of Hong Kong's Cantonese dialect, Zheng is best known for his involvement in a clampdown against protests across the border in neighbouring Guangdong province.

His two deputies have been named. The first is Li Jiangzhou, a veteran public security officer who has worked in the Liaison Office, the body that represents Beijing in Hong Kong.

Beijing's new security law says agents working for the office are exempt from Hong Kong's laws while carrying out their duties.

The opening of the new office comes little more than a day after Hong Kong announced expanded search and surveillance powers for police investigating national security crimes.

The new rules also empower Hong Kong police to order internet takedown notices if posts and comments are deemed to breach national security.

A host of US tech giants, including Facebook, Google and Microsoft have said they have stopped considering requests by Hong Kong's government for information on users because of the new law.

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