The United States has voiced horror at new files on incarceration of China's Uighur minority and said they showed that abuse was likely approved at the highest levels in Beijing.
It comes after a media consortium published leaked documents it said catalogued the violations in Xinjiang, China.
"We are appalled by the reports and the jarring images," State Department spokesman Ned Price told reporters.
"It would be very difficult to imagine that a systemic effort to suppress, to detain, to conduct a campaign of genocide and crimes against humanity would not have the blessing - would not have the approval - of the highest levels of the PRC government," he said, referring to the People's Republic of China.
Meanwhile, Germany has called for a transparent investigation into the "shocking" allegations of rights abuses targeting the Uighur minority.
In a phone call with her Chinese counterpart Wang Yi, Foreign Minister Annalena Baerbock pointed to "the shocking reports and new evidence of very serious human rights violations in Xinjiang", said a German foreign ministry statement.
Ms Baerbock "called for a transparent investigation" into the allegations, the statement added.
Several media outlets earlier published leaked documents called the Xinjiang Police Files which appear to show thousands of photographs from inside Xinjiang's system of mass incarceration, including many detained Uighurs.
The youngest was only 15 at the time of her detention, say the reports.
The allegations came as UN rights chief Michelle Bachelet begins her visit to the western region to try to shed light on the plight of the Uighurs.
Campaigners accuse China's ruling Communist Party of detaining over one million Uighurs and other Muslim minorities in the far-western region, part of a years-long crackdown the United States and lawmakers in other Western countries have labelled a "genocide".
China vehemently denies the allegations, calling them the "lie of the century".
A police database obtained by AFP earlier this month listed the names and details of thousands of detained Uighurs.
Inside Xinjiang: China cracks down on Uighur population