The top legislature approved a decision on Thursday afternoon on establishing and improving the legal system and enforcement mechanisms for the Hong Kong Special Administrative Region to safeguard national security.

The national security legislation for the Hong Kong SAR is designed to ensure steady implementation of "one country, two systems" in the SAR as well as uphold its long-term stability and prosperity, Premier Li Keqiang said at a news conference following the closure of the third session of the 13th National People's Congress.

Li said the principle of "one country, two systems" is the country's basic policy and the central government has always stressed the need to fully and faithfully implement the principle, under which Hong Kong people administer Hong Kong with a high degree of autonomy.

The adoption of the decision marks a major measure to further perfect the principle of "one country, two systems", said Li Zhanshu, chairman of the 13th NPC Standing Committee, at the closing meeting of the annual session.

The NPC Standing Committee will soon formulate related laws for Hong Kong as authorized by the decision in order to safeguard national security and sovereignty and ensure Hong Kong's stability and prosperity, he said. The decision is in accordance with China's Constitution and Hong Kong's Basic Law and applies to the fundamental interests of all Chinese people, including Hong Kong compatriots, Li Zhanshu said.

United States Secretary of State Mike Pompeo said in a statement on Wednesday that the legislation will undermine Hong Kong's autonomy and freedoms and notified the US Congress that the Trump administration no longer regards Hong Kong as an autonomous region.

The Commissioner's Office of China's Foreign Ministry in Hong Kong firmly opposed and rebutted the statement on Thursday, saying such an accusation is purely defamation and distortion of the "one country, two systems" principle.

The legislation is the responsibility of the central government and targets only very few acts that seriously endanger national security without impairing Hong Kong's high degree of autonomy or the legal rights and freedoms of Hong Kong people, the office said.

Over decades, the US has called Hong Kong "a bastion of liberty" and attempted to use the "Hong Kong model" to change the social system on the Chinese mainland to split, subvert, penetrate and destroy the mainland, proving that the NPC's decision to enact a national security law is imperative and urgent, it said.

The Hong Kong and Macao Affairs Office of the State Council said the approval of the decision fully demonstrates the strong will and firm determination of the entire Chinese people against foreign interference in terms of safeguarding national security.

The national security legislation will be a "high-hanging sword" for the very few acts that endanger national security while serving as a system of protection for the majority of Hong Kong residents, the office said.

It ensures that the high degree of autonomy, independent judicial system and right to final adjudication will not change, and Hong Kong will remain open to foreign investors with a more safe, stable and harmonious environment, the office said. Hong Kong also will maintain its status as an international financial, trade and shipping center.

The Liaison Office of the Central People's Government in the HKSAR said in a statement on Thursday that the office firmly supports the endorsement of the decision by the country's top legislature to enact a national security law for the city, adding it shows the shared wishes of Chinese people.

"It means a lot to Hong Kong's long-term stability and prosperity and the successful practice of the 'one country, two systems' principle," the statement said.

Expecting the legislative work to be done as soon as possible, the office said it will take on its role to reflect Hong Kong people's opinions. The office believed that Hong Kong will be back on the right track, and residents will see the return of a peaceful life under the protection of the law, according to the statement.

Hong Kong Chief Executive Carrie Lam Cheng Yuet-ngor said in a statement on Thursday afternoon that she welcomes the approval of the decision by the NPC considering the urgent need to improve Hong Kong's legal system at the State level.

She said the SAR government will fully cooperate with the NPC Standing Committee to advance legislation as soon as possible and proactively reflect the detailed situation in Hong Kong during the process.

"I strongly believe that various sectors of society will lend their full support for the legislation," Lam said, adding that the government will also ramp up enforcement of the national security law, raise public awareness of the law and report regularly to the central government.

Lam reassured Hong Kong residents that the legislation won't affect the legitimate rights and freedoms they are entitled to, but only prevent, curb and sanction an extremely small minority of criminals who threaten national security.

The increasing national security risks in Hong Kong have become a prominent problem, especially unrest triggered by the now-withdrawn extradition bill starting last June. The SAR also failed to complete its own legislation on national security as required by Article 23 of the Basic Law, which stipulates that Hong Kong shall enact laws on its own to prohibit any act of treason, secession, sedition or subversion against the central government, theft of State secrets or conspiring with foreign forces.

The NPC deputies said the decision is a "very necessary and timely" move and, from a legal point of view, the use of legal methods to maintain national security is beyond reproach for any country.

Ma Yide, a law professor at Zhongnan University of Economics and Law and an NPC deputy, said the decision has a full legal basis.

"The premise and foundation of 'one country, two systems' is 'one country'. When Hong Kong residents' rights to live and work are affected, the central government should 'wield the sword'," he said, adding that China has every right to defend its integrity, resolve internal affairs and prevent any act of foreign interference.