A Hong Kong internet service provider has for the first time blocked a pro-democracy website under a new security law, raising concerns the financial hub is implementing mainland China-style limits on internet freedom.

Hong Kong Broadband Network, one of the city’s main internet providers, said on Thursday it had disabled access to the website, HKChronicles, after a request from authorities issued under the national security law. The provider said it blocked the site on Wednesday.

Mainland China restricts access to most of the web and censors social media in real time in a practice known as the Great Firewall of China. Hong Kongers, however, enjoy free internet access, which is seen as essential for global businesses using the territory as a regional hub.

HKChronicles became controversial for publishing the personal details of pro-government figures and police and their families, a process known as “doxing”, and for providing information on Hong Kong’s 2019 anti-government protests.

Beijing imposed the new security law on Hong Kong last year after the demonstrations, which often ended in violent clashes.

But analysts said the blocking of HKChronicles could be a sign the government was planning more internet censorship.

“Hong Kong is a city built on freedom, free markets and a free internet. But if the Hong Kong government censors the internet, more people and companies might leave the city,” said Lokman Tsui, assistant professor at the School of Journalism and Communication at the Chinese University of Hong Kong.

David Bonderman and James Coulter, the billionaire co-founders of buyout firm TPG, are substantial shareholders in Hong Kong Broadband Network, through TPG Asia Advisors VI and TPG Wireman. Canada Pension Plan Investment Board and Capital Group, the investment manager, are also big shareholders.

Capital Group and CPPIB declined to comment. Mr Bonderman and Mr Coulter were contacted for comment.

Naomi Chan, the chief editor of the website, first suspected it had been blocked last week. “After discussing and investigating with our supporters, we found that some ISPs of Hong Kong had deliberately dropped any connection to our servers, so that the users could not receive replies from our servers, resulting in an inability to access our content,” she said in a statement posted on her website.

“Hong Kongers [should] make early preparations to counter future internet blockage[s] at a larger scale, and to face the darkness before dawn,” she added.

Paul Haswell, a partner at international law firm Pinsent Mason, said while he expected authorities to make increasing use of their new powers, he thought that Chinese-style censorship was “still a long way from encircling Hong Kong".

“There is also the considerable inconvenience and harm that would be caused to businesses in Hong Kong if the Great Firewall were to be implemented here,” he added, “and users could no longer access the likes of Google, Facebook and so on — something that the Hong Kong government would be keen to avoid.”

The security law has spooked parts of Hong Kong’s business community, leading international chambers of commerce representing global banks and multinationals to formally ask the Hong Kong government for more clarity on its application.

The law, which targets subversion, collusion and foreign interference, has been criticised as too vague and carries penalties of up to life imprisonment.

The protests last year erupted in response to an extradition law that would have allowed criminal suspects to be transferred to the mainland. They grew to include concerns over Beijing’s increasing influence in the city and threats to freedoms guaranteed to Hong Kong on its handover from the UK to China in 1997.