The State Council's Hong Kong and Macao Affairs Office has strongly condemned the signing of legislation known as the Hong Kong Human Rights and Democracy Act of 2019 into law in the United States.

US President Donald Trump signed the act into law on Wednesday despite China's strong opposition.

The HKMAO described it as gross interference in China's internal affairs and a serious violation of international law and the basic norms of international relations.

The act, condemned by the Chinese people, including Hong Kong compatriots, is full of prejudice and arrogance and treats Hong Kong with intimidation and threats, the office said in a statement released on Thursday. It blatantly offers protection to Hong Kong rioters and separatists, showing malicious intent, the statement said, adding that the US has been proven to be the biggest manipulator behind the chaos in Hong Kong.

It said the Chinese government is determined to unswervingly safeguard the nation's sovereignty, security and interests, to implement the "one country two systems" principle and to oppose any external forces trying to interfere in Hong Kong affairs.

"The US trying to mess up Hong Kong in order to curb China's development is just a futile attempt," the office said. "Hong Kong's future and destiny are always in the hands of Chinese people, including Hong Kong compatriots.

"No force can stop the Chinese nation from achieving great rejuvenation."