A music producer was jailed for five years on Monday for taking part in a riot described by a District Court judge as a beautiful sight for foreign politicians, but a moment of grief for Hongkongers.

Mok Chun-yu, 36, was earlier found guilty of throwing bricks during a protest in Admiralty on September 29, 2019.

Passing sentence, judge Stanley Chan rejected Mok's claim that he had no plans to take part in the protest, saying he was heavily geared up with a helmet, gas mask and arm guards.

Chan said it was an aggravating factor that protesters were rioting around the government's headquarters and the Legislative Council complex and they were directly challenging the core powers of Hong Kong and China.

He said the violence was shocking as it involved many strongly organised rioters and it was like a warzone that aggrieved law-abiding Hong Kong people, but was a beautiful sight to behold for foreign politicians.

Chan said the date of the riot was politically sensitive, as it was just two days before National Day.

The judge added that a deterrent sentence was needed in this case to send a message to those who use the internet to advocate violence.