A Hong Kong court has sentenced the first two people under a tough new Hong Kong national security law, including a man who was given 14 months in prison for wearing a T-shirt with a protest slogan.

A Hong Kong man convicted for wearing a "seditious" T-shirt last year was sentenced to 14 months in jail under the city's new security law that continues to crack down on supporters of anti-government demonstrations.

Hong Kong’s new security law is “unambiguous” about what counts as unlawful seditious acts, the city’s government has said, after a man was sentenced to 14 months in jail in the first conviction under the legislation.

A Hong Kong court has sentenced a third person convicted of sedition under the domestic national security law to 14 months in prison, ruling he defied the nation’s sovereignty and instigated hatred towards officials with persistent calls for “dictators” Xi Jinping and John Lee Ka-chiu to step down.