The U.S.' 2023 Hong Kong Policy Act Report, published by the U.S. State Department, said Chinese and Hong Kong authorities "continued to use 'national security' as a broad and vague basis to undermine the rule of law and protected rights and freedoms."

China imposed a national security law on Hong Kong in June 2020 without any local legislative or consultative process, outlawing crimes such as subversion with possible life imprisonment.

Authorities say the law restored order after protracted pro-democracy protests in 2019, that called for, among other demands, full democracy.

The city's tougher security regimen mirrors mainland China, where Chinese leader Xi Jinping has implemented a fierce crackdown on dissent over the past decade, jailing critics and rights defenders.

"Hong Kong authorities continued to arrest and prosecute people for peaceful political expression critical of the local and central governments, including for posting and forwarding social media posts," the U.S. report said.

A Hong Kong government spokesperson, however, said in a statement that it "strongly disapproved of and firmly rejected the unfounded and fact-twisting remarks" in the report.

"The U.S.' attempt to undermine the stability and prosperity of Hong Kong will only expose its own weakness and faulty arguments and be doomed to fail."

The spokesperson added the safeguarding of national security was of "cardinal importance" and all people are equal under the law regardless of political stance or background.

Over 230 people have been arrested for alleged acts endangering national security since 2020, including 47 prominent democrats now battling subversion conspiracy charges in a landmark trial that will continue for several months.

The U.S. report also noted a drop in the number of U.S. citizens in Hong Kong from 85,000 in 2021 to around 70,000 due to a number of factors including tight Covid restrictions and national security.

China "increasingly exercised police and security power in Hong Kong, subjecting U.S. citizens who are publicly critical of the PRC (China) to a heightened risk of arrest, detention, expulsion, or prosecution in Hong Kong," the report wrote, adding these risks had been highlighted in its government travel advisories for Hong Kong.

Forty of the 100 U.S. senators co-sponsored a resolution earlier this month urging a strong U.S. government response to any Chinese efforts to clamp down on dissent in Hong Kong, including the use of sanctions and other tools.