Giving cash to mosques, failing to chat to to neighbours, and walking in public without authorisation have been revealed as the seemingly mundane reasons for police investigations of Muslims in west China’s Xinjiang region.

Human Rights Watch (HRW) made changes to a police app to reveal the scores of seemingly lawful acts that officers record on phones then link to a mass surveillance database.

The United Nations believes at least a million Muslims in the vast region have been detained by Chinese authorities in “re-education” centres.

Beyond the detainment camps, many Xinjiang citizens are believed to be under house arrest or barred from entering public spaces. The app can track individuals’ movements and alert officers when they enter public spaces without permission.

Other “suspicious” behaviour listed includes giving petrol to friends, but also failing to “socialise with neighbours”. Further red flags include collecting “money or materials for mosques with enthusiasm”, getting a new phone number, and using “abnormal” amounts of electricity.

Police are prompted to check if citizens use foreign messaging apps such as WhatsApp and Telegram, which are harder for authorities to monitor and censor than domestic apps. HRW said that using such apps has resulted in individuals being detained in Xinjiang.