Police said HK$18 million (US$2.3m) in Apple Daily assets had also been frozen under the security law, the first time a seizure order has been made directly against a Hong Kong media company, rather than an individual. They may appear in court as soon as Saturday.
"The action targeted the use of journalistic work as a tool to endanger national security", he said. Apple Daily founder Jimmy Lai is now serving a 20-month prison sentence after being convicted of playing a role in unauthorized protests in 2019, when Hongkongers took the streets in massive antigovernment demonstrations in response to a proposed extradition law that would have allowed suspects to stand trial in China.
According to the BBC's Danny Vincent, this incident marks the first time Hong Kong journalists have been arrested under suspicion of violating the national security law.
Britain and its allies say the national security law breaches the "one country, two systems" principle enshrined in the 1984 Sino-British treaty that guaranteed Hong Kong's autonomy.
Sunny Cheung, an activist who has been in exile from Hong Kong after a warrant was issued for his arrest, told Fox News in a phone call that the raid shows the Chinese Communist Party's effort to repress press freedoms.
The U.S. and Japan also spoke out about the arrests.
A Hong Kong police official said the collusion charge was in relation to over 30 articles published by the outlet since 2019 that sought to have foreign countries impose sanctions on China or Hong Kong.
A features reporter, who gave her surname Chan, said gallows humour had descended over the newsroom in recent months. "Some external forces, however, have exploited the cases and distorted the truth, smearing Hong Kong's press freedom and even spreading rumor about so-called 'chilling effects'".
Apple Daily founder Jimmy Lai is serving a prison sentence for his involvement in unauthorized assemblies in 2019.
Furthermore, it called on the Hong Kong authorities to recognise that journalism is not a crime and that journalists should not be criminalised simply for doing their jobs. Last month, authorities froze Lai's assets and shares in Next Digital. He added: "Distance yourself from them, otherwise all you will be left with are regrets".
He admitted that the paper was in "crisis" since the jailing of its owner but said his reporters were determined to press on with publishing. The result is that it has virtually silenced opposition voices in the city - and drawn sanctions from the USA against Hong Kong and Chinese government officials.
Apple Daily broadcast live footage of the raid showing officers searching the newsroom and looking through journalists' computers.
The raid "further demonstrates how the national security law is being used to stifle media freedom and freedom of expression in Hong Kong", EU spokesperson Nabila Massrali said in a statement.
Reuters reported that trading for the company's stock on the Hong Kong bourse was suspended on Thursday.