The Chinese embassy in London said "all Chinese compatriots residing in Hong Kong are Chinese nationals" responding to UK's remarks on offering citizenship to Hong Kongers amid the new security law in the country.
China is warning Britain it could retaliate with "corresponding measures" for London's decision to extend a broader path to citizenship for the residents of Hong Kong.
Britain's offer came in response to a sweeping new security law that China unveiled for the former British territory this week.
Hong Kong was under UK jurisdiction until it was handed over to China in 1997 with a guarantee that Beijing would preserve the city's judicial and legislative autonomy for 50 years.
The Chinese embassy in London on Wednesday stressed that "all Chinese compatriots residing in Hong Kong are Chinese nationals".
The British plan covers almost three million Hong Kongers who either have a British National Overseas (BNO) passports or are eligible to apply for one.
In the meantime, Taiwan's government advised citizens to avoid unnecessary visits to or transit through Hong Kong, Macau or mainland China amid the new law.
Speaking to reporters in Taipei, Chiu Chui-Cheng, deputy head of Taiwan's Mainland Affairs Council, said the law was the "the most outrageous in history" with a reach that extended everywhere.
READ MORE: China's security law in Hong Kong explained
The Chinese embassy said the people in Hong Kong were Chinese nationals as well.
"If the British side makes unilateral changes to the relevant practice, it will breach its own position and pledges as well as international law and basic norms governing international relations," it said in a statement.
"We firmly oppose this and reserve the right to take corresponding measures," it said without elaborating.
Beijing has never publicly raised the possibility of offering Britons either Chinese citizenship or broader residence rights.
The Chinese statement concluded by urging London to reassess its decision and "refrain from interfering in Hong Kong affairs in any way".
Under a deal ahead of the handover from Britain, authoritarian China guaranteed Hong Kong civil liberties as well as judicial and legislative autonomy until 2047 in a formula known as "One Country, Two Systems".
Critics – including Britain – say the new law demolishes that deal, especially as China says it will have jurisdiction over some cases and has empowered its security agents to operate openly inside Hong Kong for the first time.
Britain had sought closer relations with China after ending its decades-long membership in the European Union this year.
Prime Minister Boris Johnson's government also irritated the US administration in January by allowing the private Chinese telecoms group Huawei to unroll Britain's speedy new data network.
But Britain is now studying ways it can cut Huawei out of its system entirely and build up an alliance of European and Asian providers that reduces China's dominance in the field.
UK media said the Foreign Office summoned the Chinese ambassador to London on Wednesday to express its concerns about the law.
Foreign Secretary Dominic Raab later conceded there would be little London could do if China refuses to allow Hong Kongers to relocate to Britain.
"Ultimately, if they follow through on something like that there would be little that we could do to coercively force them," Raab told ITV television late on Wednesday.
Raab said London could use "diplomatic leverage (and) other ways" to try to soften China's approach to Hong Kong and not follow through on the full force of the sweeping new security law.
Chinese authorities arrested 10 people and detained more than 300 under the new legislation during protests on Wednesday marking the anniversary of Hong Kong's return to China.
"But ultimately we need to be honest that we wouldn't be able to force China to allow BNOs to come to the UK," Raab said.
Today I updated the House on the grave and disturbing situation in Hong Kong. We will continue to bring together our international partners to stand up for the people of Hong Kong, to call out the violation of their freedoms, and to hold China to their international obligations. pic.twitter.com/Yj27b8aAfO— Dominic Raab (@DominicRaab) July 1, 2020
Australia an opportunity for Hong Kongers?
Australia's Prime Minister Scott Morrison said his government was considering an offer of safe haven to Hong Kong residents threatened by China's new law.
Morrison said Cabinet would soon consider options "to provide similar opportunities" as British Prime Minister Boris Johnson has offered people in Hong Kong.
Australia could potentially offer Hong Kong residents temporary protection visas that allow refugees to live in the country for up to three years.
An offer of safe haven to Hong Kong residents would further strain relations between Australia and its most important trading partner, China.
READ MORE: China's security law in Hong Kong explained
Hong Kong Bar Association gravely concerned over law
Hong Kong's Bar Association has warned the new law undermines the city's independent judiciary and stifles freedoms.
In a scathing critique, the group detailed how the new law dismantles the legal firewall that has existed between Hong Kong's independent judiciary and China's Communist Party-controlled courts since the 1997 handover.
The legislation outlawing acts of subversion, secession, terrorism and colluding with foreign forces was passed on Tuesday in Beijing, bypassing Hong Kong's legislature, its wording kept secret until it was enacted later that day.
In a five-page analysis, the Bar Association said the new national security offences were "widely drawn" and "are capable of being applied in a manner that is arbitrary, and that disproportionately interferes with fundamental rights, including the freedom of conscience, expression and assembly".
"In addition to the total absence of meaningful consultation, lawyers, judges, police and Hong Kong residents were given no opportunity to familiarise themselves with the contents of the new law, including the serious criminal offences it creates, before it came into force," the analysis added.
It has also claimed global jurisdiction, saying the law covers national security offences committed overseas – even by foreigners.
Rendition, not extradition
The Bar Association said the law makes clear "suspects can be removed to face trial in Mainland China" and points out that the process does not have the usual checks and balances of extradition hearings.
Instead, it looks more like rendition – when a person is simply taken to another jurisdiction.
It noted the law allowed mainland security agents working in Hong Kong to be "above the reach of local law" and said empowering the city's chief executive to appoint judges to oversee national security cases undermined judicial independence.
Local police have been granted wider surveillance powers to monitor suspects, including wiretapping, without a judge's approval, the association added.
It also expressed concern that some national security trials could be heard behind closed doors, without juries, and that Beijing – not Hong Kong's courts – has final say interpreting the new law.