Refusing to comply could lead to up to one year's jail and a fine of up to HK$100,000 ($A18,000) while providing false or misleading information could bring up to three years' imprisonment and a fine of up to HK$500,000.
The city government on Monday gazetted the new amendments to the implementation rules of the national security law imposed by officials in Beijing in 2020, using powers to bypass Hong Kong's legislature.
Officials will brief lawmakers on Tuesday, a government statement said.
The sweeping law punishes acts, including subversion and collusion with foreign forces, with up to life imprisonment.
It sparked criticism from some foreign governments and rights groups but Chinese and Hong Kong officials said it was needed to restore stability after the city was rocked by months of pro-democracy protests in 2019.
The new amendments empower police to require a person under investigation suspected of endangering national security to provide any password or decryption method for electronic devices and to provide the police "any reasonable and necessary information or assistance".
The new amendments also empower customs officers to seize items that are deemed to have "seditious intention," regardless of whether any person has been arrested for an offence endangering national security because of the items.
Urania Chiu, a law lecturer in the United Kingdom researching Hong Kong, said the new provisions interfered with fundamental liberties including the privacy of communication and the right to a fair trial.
"The sweeping powers given to law enforcement officers without any need for judicial authorisation are grossly disproportionate to any legitimate aim the bylaw purports to achieve," Chiu said.
A Hong Kong government spokesperson said the amended rules conform to the city's mini-constitution, the Basic Law, and its human rights provisions, and "will not affect the lives of the general public or the normal operation of institutions and organisations".
According to the Security Bureau, a total of 386 people have been arrested for national security crimes, with 176 people and four companies convicted.
Hong Kong media tycoon Jimmy Lai was sentenced to a 20-year jail term in February for collusion with foreign forces and sedition, sparking international criticism.
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