Hong Kong police arrested and detained five Apple Daily newspaper executives Thursday. Police also raided the newspaper's main office with a warrant to seize journalistic materials issued under the city's new national security law.

The seizure warrant was the first to be issued under the security law, which was imposed last year. Police officials said articles published by the newspaper violated the security law.

Around 500 police officers participated in the raid on the office of the pro-democracy tabloid. It was the latest blow to media tycoon Jimmy Lai, who is currently serving a prison sentence for his participation in illegal assemblies.

All of Lai's personal assets have been seized under the new national security law. Lai previously said police had frozen more than $2.32 million of assets owned by his companies linked to Apple Daily.

Lai's legal team slammed the arrests and the seizure of the company's properties. This was the second time Apple Daily's headquarters has been raided. The office was raided last year when Lai was arrested on suspicion of colluding with foreign forces.

"This is a blatant attack on the editorial side of Apple Daily. They're arresting the top editorial folks," Lai's legal adviser, Mark Simon, said.

Apple Daily sources said police had arrested the newspaper's editor-in-chief Ryan Law, chief executive officer Cheung Kim-hung, chief operating officer Chow Tat-kuen, Deputy Chief editor Chan Puiman and Chief Executive editor Cheung Chi-wai.

Apple Daily published several photos and a live feed video of the raid on its Facebook page. Police were showed sitting at reporter's desks and using their computers. One photo showed the company's chief editor being walked out in handcuffs and flanked by police.

Sources said police officers seized computers and the personal phones of reporters during the raid. Police said they were gathering the devices as evidence to be used in a case against the newspaper.

Legal experts said the national security law is not retrospective but prosecutors can still use the devices as evidence. Police said "dozens" of articles published by the newspaper since 2019 may be a violation of the new security law.

 "The nature of the articles is very simple: inciting, requesting foreign countries to impose sanctions on Hong Kong and the People's Republic of China. Very straightforward," Hong Kong police senior superintendent, Li Kwai-wah, said.