“The unknown fate of Abuduwaili Abudureheman is deeply worrying, given the background of crimes against humanity committed against Uyghurs by the Chinese government in Xinjiang, and its ongoing pursuit of Uyghurs who have travelled overseas,” Amnesty International China researcher Alkan Akad said in a statement. He said the student appears to have been detained and interrogated, and that raised questions about the Hong Kong government's possible involvement in human rights violations committed against Uyghurs by the Chinese government.

The Hong Kong government did not immediately respond to a request for comment. Hong Kong is a former British colony that returned to Chinese rule in 1997 with a promise that it could retain its Western-style freedoms and autonomy for 50 years. But critics say Beijing is increasing its control over the territory and reducing its liberties. The United Nations and human rights groups accuse China of detaining a million or more Uyghurs and members of other predominantly Muslim groups in camps where many have said they were tortured, sexually assaulted and forced to abandon their language and religion.

China denies the accusations, which are based on interviews with survivors and photos and satellite images of the Xinjiang region where many Uyghurs live. Amnesty International said it understood that Abuduwaili Abudureheman, who has been studying in Seoul for seven years, was on a Chinese government “watch list” because of his history of overseas travel, and urged Hong Kong authorities to reveal his whereabouts.

“(He) is at grave risk of torture based on his ethnicity and religion. If he is detained, he must be provided with access to a lawyer and relatives, and protected against any ill treatment,” Akad said.