image copyrightGetty Imagesimage captionApple Daily editor-in-chief Ryan Law

Hong Kong police arrested the editor-in-chief and four other executives of pro-democracy newspaper Apple Daily on Thursday, on suspicion of violating the national security law.

Apple Daily is owned by media mogul Jimmy Lai, who was also arrested and jailed on a string of charges.

Apple Daily is known to be critical of Beijing's leadership.

Dozens of prominent activists have been arrested since the national security law was introduced last year.

What happened on Thursday?

Police entered the Apple Daily office premises at around 07:30 local time on Thursday (23:30 GMT Wednesday) and blocked off all entrances and exits,

The paper broadcasted live footage of the raid on its Facebook account.

Police said in a statement that they conducted a search operation at a media company, adding that their warrant "covered the power of searching and seizure of journalistic materials".

The police separately visited the homes of editor-in-chief Ryan Law, parent company Next Digital's CEO Cheung Kim-hung, COO Chow Tat-kuen, Apple Daily publisher Chan Pui-man and Director Cheung Chi-wai, and arrested them.

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Police did not name those arrested but confirmed that the five people, aged between 47 and 63, were arrested for "collusion with a foreign country or with external elements to endanger national security".

This is the second raid to take place in Apple Daily in under a year – a raid last August saw 10 people arrested including Lai and his sons.

Who is Jimmy Lai?

Lai is one of the most prominent supporters of Hong Kong's pro-democracy movement.

Estimated to be worth more than $1bn (£766m), he made his initial fortune in the clothing industry and later ventured into media and founded Next Digital.

In his last interview with the BBC before he was sentenced to jail, he said he would not give in to intimidation.

media captionJimmy Lai: The Hong Kong billionaire becomes emotional as he faces prison

"If they can induce fear in you, that's the cheapest way to control you and the most effective way and they know it. The only way to defeat the way of intimidation is to face up to fear and don't let it frighten you," he said.

He is currently facing time in jail for a series of charges, including participating in an unauthorised assembly in 2019.

What is the national security law?

Britain handed back Hong Kong to China in 1997, and the Basic Law was created under the handover agreement under the "one country, two systems" principle.

This is supposed to protect certain freedoms for Hong Kong: freedom of assembly and speech, an independent judiciary and some democratic rights – freedoms that no other part of mainland China has.

But fears that this model was being eroded led to huge pro-democracy protests in 2019.

Some protests turned violent and in 2020, China introduced the national security law in the territory.

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Beijing said the law would target "sedition" and bring stability. Since the law has been enacted in June, around 100 people have been arrested.