Geneva: UN human rights chief Michelle Bachelet called on China on Monday to allow in monitors after "deeply disturbing" allegations of large re-education camps in which Uighurs are detained in Xinjiang province.
Her appeal for access came as Human Rights Watch reported that the Turkic, mostly Muslim Uighur minority in Xinjiang face a mass security crackdown.
A United Nations rights panel said last month it had received credible reports that up to one million Uighurs may be held in extra-legal detention in the far western province of China, and called for them to be freed.
China has rejected the allegations of internment camps and accused "external factors" of causing turbulence in the restive region.
Bachelet, a former Chilean president making her maiden speech to the UN Human Rights Council, said the panel had brought to light "deeply disturbing allegations of large-scale arbitrary detentions of Uighurs and other Muslim communities, in so-called re-education camps across Xinjiang".
Reports had been received of "patterns of human rights violations in other regions", she said.
Bachelet called on the Beijing government to permit access for her staff across China, saying that she expected discussions to start soon.
There was no immediate comment from the Chinese delegation to the council.
Countries are due to respond to her speech on Tuesday.
Bachelet promised to be a voice for victims.
"I have been a political detainee and the daughter of political detainees. I have been a refugee and a physician - including for children who experienced torture and the enforced disappearance of their parents," she told the 47-member forum in Geneva.
Bachelet voiced concern that 500 migrant children in the United States taken away from their parents have not yet been returned by authorities. She decried the announcement by US President Donald Trump's administration last week that it would withdraw from a court agreement limiting detention of migrant children to 20 days.
She urged the Saudi-led military coalition in Yemen to show greater transparency in its rules of engagement and hold to account perpetrators of air strikes on civilians, including one that hit a bus killing dozens of children in Saada last month.
"I will be closely following what steps are taken to hold the perpetrators accountable and provide remedy and compensation to the victims," she said.
Independent rights investigators reported last month that some coalition air strikes in Yemen may amount to war crimes.
The investigators gave her a confidential list of suspects linked to international crimes in the conflict, Bachelet said.
"The recent Saudi royal order which appears to provide a blanket pardon to members of the Saudi armed forces for actions taken in Yemen is very concerning," she said.