Books written by prominent Hong Kong democracy activists have started to disappear from the city's libraries, online records show, days after Beijing imposed a draconian national security law on the finance hub.
Among the authors whose titles are no longer available are Joshua Wong, one of the city's most prominent young activists, and Tanya Chan, a well known pro-democracy lawmaker.
Beijing's new national security law was imposed on Tuesday and is the most radical shift in how the semi-autonomous city is run since it was handed back to China by Britain in 1997.
China's authoritarian leaders say the powers will restore stability after a year of pro-democracy protests, will not stifle freedoms and will only target a "very small minority".
But it has already sent fear coursing through a city used to speaking openly, with police arresting people for possessing slogans pushing independence or greater autonomy and businesses scrambling to remove protest displays.
Searches on the public library website showed at least three titles by Wong, Chan and local scholar Chin Wan are no longer available for lending at any of dozens of outlets across the city.
The national security law targets acts of subversion, secession, terrorism and colluding with foreign forces. Any promotion of independence or greater autonomy appears to be banned by the legislation. Another vaguely worded provision bans inciting hatred towards the Chinese or Hong Kong government.
On the mainland, similar security laws are routinely used to crush dissent.
The new security law and the removal of books raises questions of whether academic freedom still exists. Hong Kong has some of Asia's best universities and a campus culture where topics that would be taboo on the mainland are still discussed and written about. But Beijing has made clear it wants education in the city to become more "patriotic" especially after a year of huge, often violent and largely youth-led pro-democracy protests.