Hong Kong police have offered rewards of HK$1m (£100,400; $128,000) for information leading to the arrests of five pro-democracy activists.
They include Simon Cheng, a former UK consulate employee detained in 2019 in a high-profile case.
The others are Frances Hui, Joey Siu, Johnny Fok and Tony Choi. All are accused of violating the harsh National Security Law.
The move was condemned by the US and UK where several of the activists reside.
The five individuals have been accused of various offences including "inciting secession" and "colluding with foreign forces" to endanger national security.
"They sold their country and Hong Kong, and neglected Hongkongers' interests," National Security Department Chief Superintendent Li Kwai-wah said at a press conference. "The National Security Department will pursue them until the end."
Mr Li added that the activists have continued to "engage in activities endangering national security" after they went overseas.
Mr Cheng was detained for two weeks in mainland China while on a business trip in August 2019. The former employee of the UK's Hong Kong consulate was accused of inciting political unrest in the city.
Mr Cheng told the OceanNewsUK later that year that he was "shackled, blindfolded and hooded" while under detention.
The 33-year-old was later granted asylum in the UK and went on to set up Hongkongers in Britain, a UK-wide non-profit organisation that supports Hongkongers moving to the UK.
In response to the bounty announcement, Mr Cheng said: "Being hunted by China (Hong Kong)'s secret police, under a one-million-dollar bounty, is a lifelong honour.
"If the government deems the quest for democracy and freedom a crime, we embrace the charges to reveal the genuine face of social justice, unyielding to authority," he wrote on X, the platform formerly known as Twitter.
Ms Siu said on X: "I will never be silenced, I will never back down." The 24-year-old played a key role in the Hong Kong protests of 2019 before she fled to the US.
UK Foreign Secretary David Cameron has called the Hong Kong police's move "a threat to our democracy and fundamental human rights".
"We will not tolerate any attempt by any foreign power to intimidate, harass or harm individuals or communities in the UK," he said in a statement on Thursday.
Mr Cameron added that he had instructed officials in Hong Kong, Beijing and London to "raise this issue as a matter of urgency with the Hong Kong and Chinese authorities".
In response, the Chinese embassy in the UK said it "firmly opposes the UK side's denigration of the rule of law" in Hong Kong and "its sheltering of persons on the wanted list and interference in Hong Kong-related affairs".
Meanwhile US State Department spokesman Matthew Miller said the move shows "blatant disregard" for international norms.
"We deplore any attempt to apply the Beijing-imposed national security law extraterritorially and reiterate that Hong Kong authorities have no jurisdiction within United States borders," he said.
In July, Hong Kong announced similar bounties for eight other activists, sparking international criticism.
None of them have been arrested, though authorities have detained several people accused of supporting them.
The earlier batch of wanted activists include Nathan Law, who was Hong Kong's youngest lawmaker before he was jailed for his involvement in the pro-democracy Umbrella Protests of 2014.
Human rights group Amnesty International on Thursday called on Hong Kong to withdraw the bounties and release those accused of assisting the exiled activists.
"These bounties not only threaten the liberty and safety of the activists targeted, they also have far-reaching consequences on other activists who are now left feeling increasingly uncertain about their security, whether in Hong Kong or overseas," said Sarah Brooks, the group's deputy regional director for China.
She called on host countries of the targeted activists to "protect them against long-arm persecution by the Hong Kong authorities for simply exercising their human rights".
Close to 300 people have so far been arrested under Hong Kong's controversial National Security Law. These include Hong Kong media mogul Jimmy Lai who is facing trial on Monday on allegations of colluding with foreign forces including the US.
The 76-year-old founder of now-defunct Apple Daily newspaper could be sentenced to life imprisonment if convicted.
Another 47 people including the city's most prominent activists, such as Joshua Wong and Benny Tai, are also currently on trial.
