New subsidiary legislation to Hong Kong's home-grown security law took effect on Tuesday following the Executive Council's approval, with six locations of the office overseeing national security in the city classified as "prohibited places".

The decision came a day after the government announced plans to introduce the subsidiary laws to better enable authorities to safeguard national security and address threats amid a complicated geopolitical situation.

"Against the increasingly turbulent global geopolitical landscape, national security risks to which [the Hong Kong SAR] is exposed can arise all of a sudden," a government spokesperson said in a statement.

The spokesperson went on to say the administration "must perform its constitutional duty to continue to improve the legal system and enforcement mechanisms for safeguarding national security and to formulate comprehensive measures for safeguarding national security".

The new subsidiary legislation to the Safeguarding National Security Ordinance outlaws anyone who knows or suspects that the national security office is handling a case "from disclosing to any other person any information relating to that investigation without reasonable excuse or lawful authority".

It also criminalises lying to officers and the forging of office documents.

Those found guilty of such offences could face up to seven years in prison and a maximum fine of HK$500,000.

Other new offences under the subsidiary legislation target those who wilfully resist or obstruct the Office for Safeguarding National Security in performing its duties and impersonate officers, with those convicted facing a maximum of three years behind bars and a fine of up to HK$200,000.

According to a government gazette, six sites used by the national security office have been declared as "prohibited places".

Three of the locations are on Hong Kong Island: the agency's main office at 148 Tung Lo Wan Road in Causeway Bay; 9 City Garden Road in North Point, previously the site for City Garden Hotel; and 152 Connaught Road West, the building that used to house Island Pacific Hotel.

Three other prohibited places are in Kowloon. One is 1 Cheong Tung Road in Hung Hom. The other two sites are in Tai Kok Tsui: at the junction of Hoi Fai and Sham Mong roads, and on Hoi Fan Road.

The enacted subsidiary legislation will now go through negative vetting by lawmakers.

"The [Hong Kong SAR] government will make every effort for the early completion of the scrutiny with a view to effectively safeguarding national security as soon as possible – the earlier the better," the spokesperson said.