Hong Kong libraries have taken at least nine titles written by local people or democracy advocates out of circulation pending a review of whether the books run afoul of the new national security law imposed in the city by China, a media report said today.

The Leisure and Cultural Services Department, which manages the city's public libraries, confirmed it was scrutinizing some books for compliance with the new law, without naming them, said the South China Morning Post (SCMP) newspaper report.

The Chinese books were written by activist Joshua Wong, localist Horace Chin and Civic Party lawmaker Tanya Chan.

A search of the nine titles on the library website on Saturday found all the titles marked "under review".

"A new law has come into effect so the Hong Kong authorities are reviewing these books to see if they stick to the new law or not, and under this situation the books cannot be checked out for readers now," an employee of the City Hall Public Library told the SCMP.

"After our review, then we will update the situation of the books to see if you can borrow it or not."

Beijing drafted and passed the legislation last late month that targets acts of secession, subversion, terrorism and collusion with foreign forces, with punishments of up to life in prison for the most serious offences.

It came into effect on July 2.

The move came after months of social upheaval triggered by opposition to a now-withdrawn extradition bill but that morphed into wider demands, including universal suffrage.

Mainland Chinese and Hong Kong authorities have repeatedly stressed that the law targets only a minority of residents and that the freedoms of speech and assembly will be protected.

Bar Association chairman Philip Dykes however, called the move alarming and said authorities needed to justify restricting the public's right to seek information..