The United Nations has called on China to end the detention of what it has cited as “tens of thousands to upwards of a million Uighurs” in the far western Xinjiang province.

The UN Committee on the Elimination of Racial Discrimination on Thursday urged China to “halt the practice of detaining individuals who have not been lawfully charged, tried, and convicted for a criminal offense in any extra-legal detention center.”

The committee also called out China’s practice of racial and ethnic profiling and heavy-handed restrictions that disproportionately target the Uighur community.

China has not denied the existence of the detention centers. It says the centers are part of a broader counter-terrorism and does not target a specific group.

US lawmakers on Wednesday also renewed calls for China to end its repression of minority groups in the Xinjiang region, which has become one of the most intrusive police states in the world.

Authorities use an expansive network of 40,000 facial-recognition cameras to monitor Uighur activity, and recently began collecting DNA samples, fingerprints, iris scans, and blood types from most Xinjiang residents.

Recent reports indicate the Chinese government’s surveillance efforts extend beyond its borders.

Beijing allegedly maintains a global registry of the Uighur Muslim citizens who live outside the country.