A UN human rights committee has heard there are credible reports that China is holding a million Uighurs in "counter-extremism centres".
Gay McDougall, a member of the UN Committee on the Elimination of Racial Discrimination, raised the claims at a two-day UN meeting on China.
She said she was concerned by reports that Beijing had "turned the Uighur autonomous region into something that resembles a massive internment camp".
China did not immediately respond.