In the early hours of Thursday, the University of Hong Kong dismantled and removed a statue commemorating the democracy protesters that were killed by Chinese troops around Tiananmen Square in 1989.

The eight-metre high "Pillar of Shame" by Danish sculptor Jens Galschiot had sat on the campus since 1997, the year the former British colony was handed back to China.

Ai, one of China's best known dissident artists, said he was not surprised by the statue's removal, given how dramatically Beijing is transforming Hong Kong into a mirror of the authoritarian mainland.

"(The statue) is about the truth and every moment of the Chinese Communist Party regime is about covering up and taking control of the truth," Ai told AFP.

The artist, who now lives in Germany, said he felt the city's universities had lost their autonomy under the national security law, which Beijing imposed last year after huge and often violent pro-democracy protests two years ago.

The law has criminalised much dissent and transformed the once outspoken city. Any talk of artistic freedom in this context is futile, Ai argued.

"Hong Kong is in the middle of a tempest, finding quiet and safety is impossible."

In November, Ai became the centre of attention in Hong Kong after the newly opened multimillion-dollar M+ museum decided not to display one of his photo series, which showed him flipping a finger at Tiananmen Square and other landmarks around the world.

That sparked debate about whether political art has any future in Hong Kong, which was once a regional arts hub unshackled from China's censorship.

Another dissident artist, Badiucao, represents a new generation of political illustrators, penning near-daily satire on Twitter and other social media.

Now living in Australia, he praised the "Pillar of Shame" sculpture as "absolutely a masterpiece" that served as a source of personal inspiration for him during multiple visits to the city.

"A lot of us appreciate the existence of the pillar, particularly in a university in Hong Kong. It is something that always makes us feel hope, passion and vision for the future," Badiucao told AFP. "But now this has been taken away from us."

The 35-year-old cartoonist, whose work regularly mocks Beijing's leaders, recently held his first international solo exhibition in the Italian city of Brescia, after organisers defied warnings from Chinese authorities.

Hong Kong visual artist Kacey Wong described the statue's removal as the "beginning of the Hong Kong Cultural Revolution."

Wong compared the midnight operation -- where construction workers dismantled the statue while hidden from public view -- to a grave robbery. "It is shocking to see a university fall so drastically committing a shameful act against the law and against culture and humanity under the influence of the Chinese Communist Party," said Wong, who moved to Taiwan earlier this year, citing security fears.

"The people will not forget, not the people of the free world."