Hong Kong's pro-democracy Apple Daily newspaper hit the stands Friday a day after police raided its newsroom, with an extra-large print run and a characteristic message of defiance emblazoned on its front that read: "We must press on".

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.

But those same leaders are now determined to see it silenced as they press ahead with a sweeping crackdown on dissent in Hong Kong.

More than 500 officers raided the paper's newsroom on Thursday in an operation authorities said was sparked by articles that allegedly appealed for sanctions against China.

Five executives, including chief editor Ryan Law and CEO Cheung Kim-hung, were arrested under Hong Kong's new national security law on charges of collusion.

Staff returned to a newsroom gutted of many computers and hardrives which had been carted away in police evidence bags.

But they pressed on throughout the night to get the next day's edition out, as they have for the last 26 years.

This time, they were surrounded by a gaggle of reporters from rival outlets documenting the seemingly inexorable decline of media freedoms in their city, an international media hub.

Editors settled on a simple front page featuring pictures of the five arrested executives with a straight news headline that read: "National security police searched Apple, arrested five people, seized 44 news material hard disks."

Underneath, in a bold yellow font, they printed "We must press on", words the paper said Cheung told staff as he was led away by police in handcuffs.

The company opted for a 500,000 print run - far beyond its current daily circulation of around 80,000 copies - hoping that those Hong Kongers who want a greater say in how their city is run might snap up the historic edition.

'All sold out'

In the working class district of Mongkok, dozens of residents were queuing in the early morning hours for the first edition as it was delivered to news stands.

"Usually we sell around 60 copies but tonight, we just sold 1,800," the owner of one stand, who did not give his name, told AFP.

"Now it is all sold out. We ordered 3,000 so we are still waiting for the rest to come," he added.

A 40-year-old product developer, who gave her first name Polly, said she bought ten copies.

"For many years we enjoyed the freedom of press and we were able to say anything," she told AFP. 

"But just within one year it's all different, it has deteriorated so much and everything is happening so quickly," she added.

Another customer, 45-year-old Steven Chow, snapped up three copies.

"There is no perfect media, but it (Apple Daily) is a unique voice in Hong Kong," he said. 

"You may not like it, but I think you need to let them have their voice and survive, it is important."