A man was jailed for three months on Thursday for insulting the national anthem by replacing it with a protest song in a video showing Hong Kong fencer Cheung Ka-long receiving a gold medal at the Tokyo Olympics in 2021.

Eastern Court magistrate Minnie Wat said photographer Cheng Wing-chun, 27, had shown no genuine remorse.

She said the video he posted online had been viewed 90,000 times as of last July, with some of the comments posted underneath saying the protest song, Glory to Hong Kong, is the city's real anthem.

Wat said she did not believe Cheng when he said he was not aware of the meaning of the song, given that he had worked for a political party and joined public assemblies in 2019.

In mitigation, the defence lawyer said Cheng had not committed an offence before and it is unlikely he will break the law again.

But Wat said a deterrent sentence was needed to reflect the seriousness of the offence.