UN Secretary-General Antonio Guterres, during his visit to China last week, reminded Beijing that its treatment of the Muslim Uyghurs in the troubled Xinjiang region was still under close watch, according to a UN spokesman.

China has cracked down on its population of the ethnic minority. Last year, a US State Department official estimated that at least 800,000 and possibly up to two million people may have been detained in huge “re-education centres”.

China has defended its use of what it calls vocational training centre, saying they are a necessary counter-terror measure, CNN reported.

During Guterres’ visit to the billion-dollar Belt and Road Forum in Beijing, he met China’s President Xi Jinping.

Asked by reporters on Monday whether Guterres had raised the issue of Uyghurs during that conversation, UN spokesman Stephane Dujarric replied that the UN chief had “discussed all relevant issues with Chinese authorities”.

“He did just that, and that includes the situation in Xinjiang… Each community must feel that its identity is respected and that it fully belongs to the nation as a whole,” Dujarric said, explaining Guterres’ stance.

When asked whether Guterres was satisfied by China’s response, Dujarric said: “It’s not for me to speak on behalf of the Chinese authorities.

“This is part of a dialogue that the Secretary-General has had with Chinese authorities in the past and that he will continue to have.”

In March, UN High Commissioner for Human Rights Michelle Bachelet presented a report on human rights around the world and raised the issue of “enforced disappearances and arbitrary detentions” in Xinjiang.

Later that month, Chinese Vice Foreign Minister Le Yucheng spoke to the UN Human Rights Council and defended the country’s policies in Xinjiang.

Muslims in the Xinjiang region face a multitude of restrictions, including on praying openly, wearing a veil or growing a beard.

The possession of books or articles on Islam or Uyghur culture can also be considered extremist behaviour.