Hong Kong police are investigating an incident where a crowd watching the Olympics booed China's anthem.

Hundreds gathered at a shopping mall on Monday to watch a broadcast and cheer on Hong Kong fencer Edgar Cheung, who won gold in the men's individual foil.

When the Chinese national anthem was played, some in the crowd began jeering while others shouted "We are Hong Kong", video filmed at the scene shows.

It is illegal to insult the anthem under a recently passed law.

Anyone found guilty of flouting the national anthem law could be jailed up to three years and fined HK$50,000 (£4,600, $6,400).

Reports also said that the British colonial flag was flown and some had chanted protest slogans, which could possibly violate the national security law which forbids anything that incites "secession" and could result in life in jail.

Police sources told local media that they are collecting and examining footage from the mall's security cameras.

The incident took place in the same week as the conviction of the first person charged under the national security law.

Both laws were passed last year and have been met with huge controversy, with critics saying they clamp down on free speech.

But Hong Kong authorities and the Chinese government deny this and say the laws are necessary to preserve peace and patriotism.

Hong Kong saw widespread protests in 2019 when tens of thousands took to the streets demanding democratic reforms. Some of those demonstrations turned violent as protesters and police clashed.

Since then China has cracked down hard, introducing several strict laws aimed at curbing violence and what it deems as "separatism".

Hong Kong, a former British colony, was handed back to China in 1997.

Since then it has been ruled under the "one country, two systems" principle that preserves freedoms in the city that the mainland does not have.

Critics say those freedoms are now under threat with China's recent moves and the UK has accused China of flouting the terms of its handover agreement, but China denies this.