Hong Kong police have arrested the chief editor and four executives of pro-democracy newspaper Apple Daily.
Police today raided the paper's newsroom for a second time in the latest blow to the outspoken tabloid.
The paper and its jailed owner Jimmy Lai have long been a thorn in Beijing's side with unapologetic support for the financial hub's pro-democracy movement and scathing criticism of China's authoritarian leaders.
More than 500 officers were involved in the dawn operation, which authorities said was sparked by articles Apple Daily had published "appealing for sanctions" against Hong Kong and China's leaders.
It is the first time the content of media reporting has sparked arrests under the new security law.
The union representing Apple Daily's journalists described the operation as a "wanton violation of press freedom" that "displayed how much police power has inflated under the national security law".
Officials said the five executives were arrested for collusion with a foreign country or external elements "to endanger national security".
"They have overall responsibility for the content, style and principles of news reporting," senior superintendent Steve Li told reporters.
Authorities also confirmed HK$18 million (€1.9m) in Apple Daily assets had also been frozen under the security law.
It is the first time a seizure order has been made directly against a Hong Kong media company, rather than an individual.
Hong Kong is historically a major international media hub although its press freedom ranking has slipped dramatically in recent years.
Secretary for Security John Lee declined to say which articles breached the security law or whether those who shared the articles online, bought Apple Daily or its shares, might be at risk.
"Everyone must decide for themselves," he told reporters after the arrests were made.
He rejected suggestions the operation was an assault on the media.
"Our actions are not targeting press freedom or journalistic work," he said.
"We target conspiracies that threaten national security. We target perpetrators who would use journalistic work as a tool to engage in acts that endanger national security."
Apple Daily broadcast live footage of the raid showing officers searching the newsroom and looking through journalists' computer consoles.
"Police are restricting us from using quite a lot of our equipment," an unnamed reporter said in the broadcast.
"But we can still keep this live camera on and our website will keep updating."
Among those arrested were chief editor Ryan Law and CEO Cheung Kim-hung who were both led into the building with their hands fastened behind their backs.
Hong Kong's stock exchange said trading in shares of Next Digital, the publisher of the newspaper, had been halted.
The security law introduced last June is the speartip of a sweeping crackdown on Beijing's critics in Hong Kong since 2019's huge democracy protests.
It has criminalised much dissent, given China jurisdiction over some cases and awarded authorities a suite of powerful new investigation powers.
Those convicted of a national security crime face up to life in prison and the majority are denied bail after arrest.
Thursday's raid was the second on Apple Daily in less than a year.
The tabloid's billionaire owner Mr Lai, 73, was charged with collusion after hundreds of officers searched the paper's newsroom last August.
He is currently serving multiple jail sentences for attending various protests.
Beijing has made no secret of its desire to see the paper's voice tamed, with state media routinely describing Mr Lai as a "traitor" and a "black hand" and senior communist party officials already declaring him guilty.
Last month, police used the national security law to freeze Mr Lai's bank accounts and his majority shares in Next Digital.
Until today's raid, authorities had left the company's assets alone. It is unclear whether Apple Daily will now be able to pay its staff.
"We will try all our best to publish newspapers for tomorrow," said executive chief editor Lam Man-chung, who was not among those arrested.
China says the law was needed to return stability to the international financial hub.
Critics, including many Western nations, say it has been the final nail in the coffin for the "One Country, Two Systems" promise that Hong Kong could maintain certain liberties after its 1997 handover to China by the British.
More than 100 people have been arrested under the security law, many of them the city's best-known democracy activists. Others have fled overseas.
Speaking with AFP last month, chief editor Mr Law admitted the paper was in "crisis" since Mr Lai's jailing but said his reporters were determined to press on with publishing.
At a recent meeting, staff asked Mr Law what they should do if the police came back to arrest him. "Broadcast it live," he said.