Hong Kong police have made their first arrests under a new "anti-protest" law imposed by Beijing, as crowds marked 23 years since the end of British rule.
Hundreds turned out to protest the legislation in the busy shopping district of Causeway Bay but were met with a heavy security presence.
Seven people were held accused of violating the law, including a man with a pro-independence flag. Nearly 200 others were detained at a banned rally.
Beijing's set of national security rules on Hong Kong, has ushered in a new chapter of Chinese control over the semi-autonomous territory once known as a haven of political freedom and civil liberty.
Legal experts say the most worrying aspect of the legislation is that it brings Chinese law and national security agencies to Hong Kong, eliminating the firewall separating it from mainland China under the “one country two systems” framework.
The new law came into effect in Hong Kong in the lead-up to July 1, the 23rd anniversary of the handover of Hong Kong from British rule to China. The new law broadens the powers of local and mainland authorities to investigate, prosecute and punish dissenters.
The legislation has been widely condemned by countries including the US and UK as well as human rights activists. US Secretary of State Mike Pompeo said: "[China] promised 50 years of freedom to the Hong Kong people, and gave them only 23."
Speaking in Beijing, Chinese Foreign Ministry spokesman Zhao Lijian urged countries to look at the situation objectively and said China would not allow foreign interference in its domestic affairs.
On Wednesday, Hong Kong's top official, Chief Executive Carrie Lam, said the law is a "crucial step to ending chaos and violence that has occurred over the past few months" in the city.
"The national security law is the most important development in securing ties between China and the Hong Kong Special Administrative Region since the handover," she said, framing criticism of the law as "vicious attacks."
Meawhile, UK foreign secretary, Dominic Raab, has accused China of a “clear and serious violation” of a treaty forged with the UK by imposing national security legislation on Hong Kong.
He said the UK would “honour” its commitment to citizens of the former British colony. The UK could extend the right for nearly 3 million Hong Kong citizens to come to the UK.
Under this system, the UK will grant eligible 'Hong Kongers' five years leave to remain, with a right to work or study. After these five years, people will be able to apply for settled status and, then, after a further 12 months, they will be able to apply for citizenship.
Raab said on Wednesday Beijing had breached the joint declaration signed between the UK and China to protect freedoms in the territory by enacting the controversial legislation.
What is in the new law?
The stringent new legislation and its 66 articles were kept secret from the public until the law went into effect and appear to offer the government, courts, police and authorities a roadmap to quash any hint of the mass anti-government protests that rocked the city last year.
The law applies to permanent residents and non-residents in Hong Kong who violate the law on Hong Kong territory as well as to crimes committed by a Hong Kong permanent resident outside of the city.
The law establishes four new offenses of secession, subversion, terrorism, and collusion with foreign powers. The maximum penalty for each is life imprisonment.
A terrorism charge can also include the vaguely worded provision of "other dangerous activities which seriously jeopardize public health, safety or security."
Beijing will also have power over how the law should be interpreted, and not any Hong Kong judicial or policy body. If the law conflicts with any Hong Kong law, the Beijing law takes priority.
Elsewhere, United States Secretary of State Mike Pompeo said it was a "sad day for Hong Kong, and for freedom-loving people across China" with the imposition of the national security legislation in Hong Kong.
He said the law "destroys the territory's autonomy and one of China's greatest achievements."
The EU expressed "grave concerns" that the law could "seriously undermine" the city's independence.
Taiwan's government has said it will set up a special office to help those in Hong Kong facing immediate political risks. While US lawmakers from both parties have launched a bill to give refugee status to Hong Kong residents at risk of persecution.