The US State Department on Wednesday slammed human rights violations in China, saying the sort of abuses it had inflicted on its Muslim minorities had not been seen “since the 1930s," Reuters reported.

U.S. Secretary of State Mike Pompeo highlighted abuses in Iran, South Sudan, Nicaragua and China in the department’s annual “Country Reports on Human Rights Practices,” but told reporters that China was “in a league of its own when it comes to human rights violations.”

“For me, you haven’t seen things like this since the 1930s,” Michael Kozak, the head of the State Department’s human rights and democracy bureau told the same briefing, referring to abuses of China’s Muslim minority.

The report said that in the past year, the Chinese government had significantly intensified its campaign of mass detention of members of Muslim minority groups in the Xinjiang region.

It said authorities there were reported to have arbitrarily detained 800,000 to possibly more than two million Uighurs, ethnic Kazakhs and other Muslims in internment camps designed to erase religious and ethnic identities.