China has imposed a sweeping national security law on Hong Kong, a historic move that critics and many western governments fear will suffocate the city's freedoms and reduce its relative autonomy.
Taiwan on Tuesday warned its citizens of risk in visiting Hong Kong after China's parliament passed national security legislation for the city while Taiwan's president said she was disappointed about the law.
While most cases will be heard in Hong Kong courts, suspects can be extradited to mainland China for trial under situations that are out of the Hong Kong government's control.
China promised autonomy for Hong Kong before Britain returned the territory in 1997 but wants no repeat of massive and sometimes destructive protests that rocked the territory previous year.
"It marks the end of Hong Kong that the world knew before", Wong said on Twitter.
"We will never accept the passing of the law, even though it is so overpowering", said Democratic Party chairman Wu Chi-wai.
A majority in Hong Kong opposes the legislation, a poll conducted for Reuters this month showed, but support for the protests has fallen to only a slim majority.
Lau Siu-kai, vice-president of a think-tank under the Beijing cabinet's Hong Kong and Macau Affairs Office, told Reuters the internationally criticised law was passed unanimously with 162 votes.
According to Hong Kong Chief Executive Carrie Lam, the law was to be enacted late Tuesday local time, the eve of the 23rd anniversary of Hong Kong's return to Chinese rule.
Activists have called for huge demonstrations against the law, coinciding with the 1 July handover celebration.
Dozens of supporters of Beijing popped champagne corks and waved Chinese flags in celebration in front of government headquarters.
On Friday, the state department said it was restricting visas for an unspecified number of Chinese officials seen as responsible for infringing on the autonomy of the Asian financial hub.
Months of anti-government, pro-democracy protests in Hong Kong past year won widespread sympathy in democratic and Chinese-claimed Taiwan, which has welcomed people from Hong Kong who have moved to the island and expects more to come. It follows months of anti-government protests in Hong Kong previous year that at times descended into violence.
Between the lines: The national security law manifests the Chinese Communist Party's approach to governance known as "rule by law", rather than "rule of law". Pro-China figures have also been pushing for more "patriotic" education to be introduced into the curriculum in hopes that will boost their identification with Beijing.
Hong Kongers and protest organisers say the protests, which have often resulted in violent street battles between demonstrators and police, is a manifestation of the simmering anger at the government.
Hong Kong is one of many developing conflicts between China and the United States, on top of trade, the South China Sea and the coronavirus pandemic.
However, the answer requires "strong coordination with all member states", Charles Michel, president of the European Council added.
Chris Patten, the last British governor of the territory, said the decision marked "the end of One Country, Two Systems".
Sales of VPN software, used to circumvent China's Internet censors and evade some measures of digital surveillance, have skyrocketed.