Beards and hijabs behind bars
It was easy to overlook the narrow, nondescript staircase leading to a brightly-lit basement mosque in Istanbul's busy Sultan Murat neighbourhood. Below, a small girl ran around among the white and gold columns, while a dozen men, most of them still wearing winter coats, prayed on the pale blue carpet. The men are all Uighurs, a Muslim community based in the Xinjiang Uighur Autonomous Region of north-western China.
Back in Xinjiang, these afternoon prayers would have been a dangerous act. Since 2016, the Chinese government has been arresting Uighurs and imprisoning them in what are officially called "Vocational Education Training Centres", but have been referred to in the West as "re-education" camps.
The men all raised their hands when asked how many of them have relatives in Xinjiang who disappeared into China's network of prisons and camps. They then pulled out their smartphones and showed photos of their relatives' identification cards; pictures of wives, children and parents who have disappeared without a trace.
"I don't know if my daughter is even alive or not," said one man looking at a picture of a young, slim woman.
"The Chinese government wants to take full control and eliminate all people who live there," the mosque's imam exclaimed, gesticulating angrily. "They want to kill the Uighurs and our culture."
Imprisoned for their faith and culture
It is hard to say exactly how many have been imprisoned. According to estimates, at least 1 million of the roughly 10 million Uighurs living in Xinjiang have disappeared into the network of prisons and camps constructed by Chinese authorities.
Reports from the region show that some detainees are being held indefinitely, while others are moved to labour camps. Those who are allowed to return home are kept under the close supervision of local authorities, with their freedom of movement strictly limited.
Chinese authorities claim that the "vocational training centres" were built to fight "extremist ideas" and provide Uighurs with "valuable skills". At the camps, detainees are said to undergo a rigorous indoctrination process and take Mandarin language courses.
In a recent interview during a visit to Berlin, China's Foreign Minister Wang Yi said that several NGOs, journalists and diplomats had been granted access to Xinjiang and "they didn't see a single concentration camp or re-education camp". Wang added that "there is no persecution [of Uighurs] in Xinjiang."