US Secretary of State Mike Pompeo on Friday denounced "awful abuses" of Muslim Uighurs detained in Chinese reeducation camps.
"Hundreds of thousands and possibly millions of Uighurs are held against their will in so-called reeducation camps where they're forced to endure severe political indoctrination and other awful abuses," Mr Pompeo said in a speech on the state of religious freedom around the world.
Beijing has rejected UN estimates that more than a million members of Muslim minorities are being held in internment camps in China's western Xinjiang region.
In a letter to Mr Pompeo and U.S. Treasury Secretary Steve Mnuchin, Republican and Democratic members of the U.S. Congress late last month called for sanctions on Chinese officials implicated in the internment of Uighurs.
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Mr Pompeo did not say in the speech whether he would take punitive measures.
He also expressed concern about the fate of Christians in China, who he said had been targeted in a government crackdown.
The government, he said, has been "closing churches, burning bibles and ordering followers to sign papers renouncing their faith."