The World Uyghur Congress (WUC), a human rights and advocacy organization for the ethnic group, has asked the International Olympic Committee (IOC)’s ethics commission chair to review its call for the 2022 Winter Games not to be held in Beijing, China, citing allegations of “crimes against humanity” by China against Uyghurs.

Human rights organizations and the U.N. estimate that 1-3 million Uyghurs and other Turkic Muslim minorities in China’s western region of Xinjiang have been detained in state-run camps since at least 2017 as part of a targeted crackdown on the ethnic minority groups by the Chinese Communist Party (CCP).

The World Uyghur Congress (WUC) wrote IOC ethics chief and former U.N. Secretary-General Ban Ki-moon on February 26, stating that the IOC had “acted in breach of the Olympic Charter by failing to reconsider holding the 2022 Olympics in Beijing following verifiable evidence of genocide and crimes and humanity taking place” in Xinjiang’s Uyghur detention camps.

The WUC said its previous public complaint on the issue in August 2020 had not received a fair hearing by the IOC and once again urged Ban Ki-moon to review the statement.

“The grievance requests that Mr Ban Ki Moon either examine the Complaint himself or appoint a new Ethics and Compliance Officer to do so properly,” the WUC’s press statement announcing the letter read.

Shortly after the WUC released its public complaint to the IOC last August, the body issued a statement to Reuters saying it “must remain neutral on all global political issues.”

The IOC further said it had been assured by the Chinese government “that the principles of the Olympic Charter will be respected in the context of the [2022 Winter] Games.”

The CCP officially denies the existence of detention camps in Xinjiang, though it does acknowledge placing Uyghurs and other Turkic minorities in state-run facilities since 2017; the Communist Party refers to the camps as “vocational” or “political education” centers. Beijing claims that the camps are designed to direct Uyghurs — a Turkic-speaking, Sunni Muslim minority group — into the Chinese labor force and away from alleged Islamic extremism and terrorism within Xinjiang, China’s westernmost territory. The region borders Central Asia and is referred to by Uyghurs as “East Turkestan.”

Uyghur survivors of Xinjiang’s camps and former employees of the facilities have testified to witnessing guards use “systematic” rape and sexual abuse as a form of torture against detainees. In addition, some have alleged that they experienced or witnessed forced sterilizations and abortions, slave labor conditions, and Communist political indoctrination.