The introduction of the new security law in March — four years after Beijing imposed a similar law that had all but wiped out public dissent — has deepened worries about the erosion of the city's freedoms.

The new law, known locally as “Article 23,” has expanded the government's power to deal with future challenges to its rule, punishing treason and insurrection with up to life imprisonment.

Under the legislation, offenders who commit sedition offenses face harsher penalties than before. They face a maximum jail term of seven years if convicted for committing seditious acts or uttering seditious words — up from the previous maximum sentence of two years.

Authorities raided the homes of five of the suspects and seized items including electronic devices that officers suspect were used to publish the seditious messages, police said.

When Britain handed Hong Kong back to China in 1997, Beijing promised to retain the city's Western-style liberties for 50 years. However, since the introduction of the 2020 law, Hong Kong authorities have severely limited free speech and assembly under the rubric of maintaining national security. Many activists were arrested, silenced or forced into self-exile.

The Beijing and Hong Kong governments say the China-imposed law helped return stability following huge anti-government protests in 2019