The graffiti provoked hatred, contempt or disaffection against the Hong Kong government, police said, without specifying the exact content.

Public opposition to the Hong Kong government and China in the financial hub has been essentially quashed since the introduction of two expansive national security laws in 2020 and 2024.

The 18-year-old, a part-time clerk who had just finished secondary school, appeared in court on Wednesday and was charged with committing "an act or acts that had a seditious intention", and property damage.

The man is accused of writing the graffiti on the wall of a bathroom in a commercial building over the course of July 17 to 21, AFP read in the court file.

A first conviction for the sedition offence could be punishable with up to seven years in prison, police said.

Beijing imposed a national security law on Hong Kong in 2020 after huge and sometimes violent pro-democracy protests the year before.

City officials separately passed a homegrown security law last year, under which this case is being charged.

The judge denied the accused's bail application, and the case was adjourned until August 19.

As of July 1, authorities had arrested 333 people for various national security crimes, with 165 of them convicted.