Hong Kong police have deployed a water cannon in response to a fresh protests less than 24 hours after a controversial security law was enforced by China.
More than 70 people have been arrested, with at least two detained for carrying flags calling for Hong Kong’s independence - something the new law has made illegal.
The law – which has “deeply concerned” the UK government - makes secessionist, subversive, or terrorist activities illegal, as well as foreign intervention in the city's internal affairs.
Anyone taking part in secessionist activities, such as shouting slogans or holding up banners and flags for the city’s independence, is in violation of the law regardless of whether violence is used.
A man who had a Hong Kong independence flag was arrested at a protest in the city’s Causeway Bay shopping district, police said.
ITV News Asia Correspondent Debi Edward says the actions of the police "appears to have hardened" protesters' "resolve for democracy"
Police later arrested a woman for holding up a sign displaying the British flag and calling for Hong Kong's independence
The most serious offenders, such as those deemed to be masterminds behind the crimes, could receive a maximum punishment of life imprisonment.
Lesser offenders could receive jail terms of up to three years, short-term detention or restriction.
UK Foreign Secretary Dominic Raab said national security legislation published by China “constitutes a clear violation” of the autonomy of Hong Kong.
Speaking to reporters outside the Foreign and Commonwealth Office on Wednesday, Mr Raab said: “We have very carefully now assessed the contents of this national security legislation since it was published last night.
“It constitutes a clear violation of the autonomy of Hong Kong and a direct threat to the freedoms of its people, and therefore I’m afraid to say it is a clear and serious violation of the joint declaration – the treaty between the United Kingdom and China.”
ITV News Political Correspondent Paul Brand says the UK-China relationship appears to be coming "under serious strain"
The US warned that China’s repeated violations of its international commitments “is a pattern the world cannot ignore".
And the European Union warned that China risked “very negative consequences” to its reputation and to business confidence in the global financial hub.
Hong Kong’s leader strongly endorsed the new law in her speech marking Wednesday's 23rd anniversary of the territory's handover from colonial Britain.
“The enactment of the national law is regarded as the most significant development in the relationship between the central authorities and the HKSAR since Hong Kong’s return to the motherland,” chief executive Carrie Lam said in a speech, following a flag raising ceremony and the playing of China’s national anthem.
“It is also an essential and timely decision for restoring stability in Hong Kong.”
A pro-democracy political party, The League of Social Democrats, organised a protest march during the flag-raising ceremony.
About a dozen participants chanted slogans echoing demands from protesters last year for political reform and an investigation into accusation of police abuse.
The law’s passage further blurs the distinction between the legal systems of semi-autonomous Hong Kong, which maintained aspects of British law after the 1997 handover, and the mainland’s authoritarian Communist Party system.
Critics say the law effectively ends the “one country, two systems” framework under which Hong Kong was promised a high degree of autonomy.
The law directly targets some of the actions of anti-government protesters last year, which included attacks on government offices and police stations.
Acts of vandalism against government facilities or public transit can be prosecuted as subversion or terrorism, while anyone taking part in activities deemed as secessionist would also be in violation of the new law.
Legislative Councillor for Hong Kong, Tanya Chan, warned the new law is a "white terror" that could spread to all areas of life on the island.
"I think this white terror will spread to all aspects of our normal lives and will affect not only the politicians, it will also affect normal families with kids," she told ITV News.
"Because based on the definition of national security in China, under the legislation, you can see this has very wide coverage.
"For example, economies, education, religion and all these will be affected so I’m easily worried about how far it can go.
"It seems that this piece of law is targeting just a small number of people but I don’t think so because, as I’ve mentioned it’s like a white terror - it will just spread on and will affect different types of people."