Dozens of police marched across a public square overlooking Hong Kong's harbour to face off with protesters who hurled glass bottles and rocks at them.

Earlier in the afternoon more than 1,000 people had rallied calmly, waving Uighur flags and posters, as they took part in the latest demonstration in over six months of unrest.

A mixed crowd of young and elderly people, dressed in black and wearing masks to shield their identities, held up signs reading "Free Uyghur, Free Hong Kong" and "Fake 'autonomy' in China results in genocide".

The protest comes after midfielder Mesut Ozil of English soccer club Arsenal caused a furore in China after he criticised the country's policies toward the Muslim ethnic minority in the restive northwestern region of Xinjiang.

Ozil, a German Muslim of Turkish origin, tweeted that Uighurs were "warriors who resist persecution" and criticised both China's strong hand in Xinjiang and the relative silence of Muslims in response.

United Nations experts and activists say at least 1 million Uighurs and members of other largely Muslim minority groups have been detained in camps in Xinjiang since 2017 under a campaign that has been condemned by the United States and other countries.

Beijing says it is providing vocational training to help stamp out separatism and to teach new skills. It denies any mistreatment of Uighurs.

Protests in Hong Kong are now in their seventh month, albeit in a relative year-end lull. Many residents are angry at what they see as Chinese meddling in the freedoms promised to the former British colony when it returned to Chinese rule in 1997.

The police's heavy-handed clamp-down on demonstrations and frequent use of tear gas have incensed many protesters, whose demands include full democracy and an independent investigation into perceived police brutality.

Australian Associated Press