Several former detainees from inside Uighur internment camps in China, and a guard, have told the BBC they experienced or saw evidence of an organised system of mass rape, sexual abuse and torture.

Tursunay Ziawudun, who fled Xinjiang after her release and is now in the US, said women were removed from the cells “every night” and raped by one or more masked Chinese men. She said she was tortured and later gang-raped on three occasions, each time by two or three men.

Another woman described being electrocuted as part of sexual torture: “The woman took me to the room next to where the other girl had been taken in. They had an electric stick, I didn’t know what it was, and it was pushed inside my genital tract, torturing me with an electric shock.”

A leading expert on China’s policies in Xinjiang, Adrian Zenz, told the BBC that the testimony gathered for their story was “some of the most horrendous evidence I have seen since the atrocity began”.

“This confirms the very worst of what we have heard before,” he said. “It provides authoritative and detailed evidence of sexual abuse and torture at a level clearly greater than what we had assumed.”