At a crowded press event on Friday in Beijing, Chinese officials aired a video of a thin Uighur man with a shaved head, wearing an oversized uniform and speaking directly to the camera.

"I will try my best to change myself and receive the leniency of the party and the government," says the man, Erkin Tursun, a former TV producer who, the officials said, is serving a 20-year sentence in Xinjiang on charges of "inciting ethnic hatred, ethnic discrimination and covering up crimes".

Tursun, almost unrecognisable from photos shared online before his 2018 arrest, is addressing his son, who now lives abroad and has publicly advocated...