Democracy books disappear from Hong Kong libraries

Books written by prominent Hong Kong democracy activists have started to disappear from the city's libraries in the aftermath of China imposing a draconian national security law on the finance hub.

Beijing's new national security law is the most radical shift in how the semi-autonomous city is run since it was handed back to China by Britain in 1997.

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. 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.  

China says it will have jurisdiction in some cases and empowered its security apparatus to set up shop openly in Hong Kong for the first time, ending the legal firewall between the two.

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 police have already arrested people for possessing slogans pushing independence or greater autonomy. 

Wong said he believed the removal of the books was sparked by the security law. 

"White terror continues to spread, the national security law is fundamentally a tool to incriminate speech," he wrote on Facebook.

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.