The Jiaman mosque in the city of Qira, in the far western Chinese region of Xinjiang, is hidden behind high walls and Communist Party propaganda signs, leaving passersby with no indication that it is home to a religious site.

In late April, during the Muslim holy month of Ramadan, two ethnic Uyghur women sat behind a tiny mesh grate, underneath a surveillance camera, inside the compound of what had long been the city's largest place of worship...