HONG KONG - China on Tuesday released a policy white paper on Hong Kong's practice of safeguarding national security to ensure stability in a volatile world, emphasizing Beijing has "fundamental responsibility" for national security affairs in the city.

This white paper was released by China's State Council, or cabinet, a day after a Hong Kong court sentenced leading China critic and former media mogul Jimmy Lai to 20 years imprisonment in a landmark foreign collusion case under the city's national security law.

Lai's sentence, the heaviest so far under a China-imposed national security law, drew international criticism from the U.S., Britain, Taiwan, European Union, Japan and rights groups.

The United Nations rights chief Volker Turk "deplored" the sentence of the 78-year-old and said it was "incompatible with international law".

The white paper said Hong Kong would continue to improve its legal system to safeguard national security.

"Hong Kong, enjoying high-standard security, is bound to overcome all risks and challenges on the journey forward, and remain as steady as a rock in a turbulent world," it read.

Hong Kong leader John Lee on Tuesday welcomed the white paper, saying authorities needed to remain vigilant against national security risks.

He said Lai's sentence sent a "solemn warning against malicious plots of collusion with external elements and endangering national security".

Critics say the sweeping national security law has been used to clamp down on dissent and the city's opposition pro-democracy movement after mass protests in 2019.

The white paper, however, described this law as a "legal shield" that had "neutralised this major threat" and restored order.

The paper added that Hong Kong's practice of safeguarding national security had "consolidated the security foundation" of the city's "one country, two systems" governance model and "further enriched China's national security system".

Such white paperson Hong Kong are released periodically by China, outlining Beijing's latest policy stance towards the China-ruled city that returned from British to Chinese rule in 1997.

The previous white paper in 2021 outlined Hong Kong's democratic development after a revamp of the electoral system to ensure only "patriots" could run for public office - a move criticised by some countries as an erosion of democratic freedoms by marginalising opposition democrats.

READ: NEWSMAKER: Jimmy Lai, devout Catholic and media mogul who stood up to China

-Editing by Jamie Freed and Stephen Coates/Reuters