Hong Kong police made the first arrests under Beijing's new national security law on Wednesday as the city greeted the anniversary of its handover to China with protesters fleeing water cannon.
The commemorations came a day after China imposed a sweeping security law on the city, a historic move decried by many Western governments as an unprecedented assault on the finance hub's liberties and autonomy.
Certain political views and symbols became illegal overnight, including showing support for Hong Kong, Taiwan, Xinjiang and Tibet independence.
By Wednesday afternoon police said two people had been arrested under the new law, a man and a woman both carrying Hong Kong independence signs.
"Advocacy for independence of Hong Kong is against the law," security minister John Lee told reporters.
A few thousand protesters defied a ban on rallies to gather in the shopping district of Causeway Bay on Wednesday, blocking some roads.
Riot police responded with water cannon and pepper spray, making at least 70 arrests.
"What this authoritarian regime wants to do is to terrorise the people and stop them from coming out," Chris To, a 49-year-old protester, told AFP.
Opprobrium over the law poured in from critics and western governments -- led by the United States -- over fears the law will usher in a new era of mainland-style political repression.
Under a deal ahead of the 1997 handover from Britain, authoritarian China guaranteed Hong Kong civil liberties as well as judicial and legislative autonomy until 2047 in a deal known as "One Country, Two Systems".
"(China) promised 50 years of freedom to the Hong Kong people, and gave them only 23," US Secretary of State Mike Pompeo said as he promised unspecified countermeasures.
But Beijing said foreign countries should keep quiet about the law, while Hong Kong leader Carrie Lam hailed the legislation as the "most important development" since the city's return to Beijing's rule.
After huge and often violent pro-democracy protests last year, authorities have shown zero tolerance for even peaceful rallies in recent months.
Gatherings of more than 50 people are currently banned under anti-coronavirus laws even though local transmissions have ended.
The July 1 anniversary has long been a polarising day in the city.
Beijing loyalists celebrate Hong Kong's return to the Chinese motherland after a century and a half of what they consider humiliating colonial rule by Britain.
During a morning anniversary ceremony, helicopters flew across Victoria Harbour carrying a large Chinese flag and a smaller Hong Kong pennant, while a barge appeared with a banner reading "Welcome the Enacting of the National Security Law" in giant Chinese characters.
Small groups of Beijing supporters waved Chinese flags in several local neighbourhoods, untroubled by police.
Democracy advocates have used the occasion to hold large rallies as popular anger towards Beijing swells -- although this year's event was banned for the first time in 17 years.
During huge pro-democracy demonstrations last year, the city's legislature was besieged and trashed by protesters.
The "One Country, Two Systems" formula helped cement the Hong Kong's status as a world-class business hub, bolstered by an independent judiciary and political freedoms unseen on the mainland.
But critics have long accused Beijing of chipping away at that status and describe the new security law as the most brazen move yet.
It was passed in just six weeks, skipping Hong Kong's fractious legislature, and the precise wording was kept secret until it came into effect late Tuesday.
It outlaws subversion, secession, terrorism and colluding with foreign forces to undermine national security, with sentences of up to life in prison.
It also topples the legal firewall that has existed between the city's judiciary and the mainland's party-controlled courts.
China will have jurisdiction over "serious" cases and its security agencies will also be able to operate publicly in the city for the first time.
Another provision also claims universal jurisdiction for national security crimes committed beyond Hong Kong or China.
More than two dozen countries -- including Britain, France, Germany and Japan -- urged Beijing to reconsider the law, saying it undermines the city's freedoms.
Canada, meanwhile, warned citizens in Hong Kong that they faced an increased risk of arbitrary detention or even extradition to China.
In Taiwan, authorities there opened a new office to deal with Hong Kongers seeking refuge.
Beijing says the law will restore stability after a year of pro-democracy protests and will not end Hong Kong's freedoms.
But critics have little faith in those assurances given how similar national security laws are routinely used on the mainland to crush dissent.
Hong Kong, China | AFP