In mid-October, the public security bureau in the city of Shihezi posted a directive on a verified social media account asking residents to hand in their passports to police.

It stated: “Those who refuse to hand them in will bear the responsibility themselves should there be consequences such as being forbidden to go abroad.”

The post was later deleted.

Photos of other notices posted on social media showed police stations in various counties and in the regional capital, Urumqi, requesting citizens to hand in passports or stating that new documents would no longer be issued.

Angry questions about the new restrictions abounded on Chinese social media.

“I didn’t spend time and money getting a passport to become the focus of the government’s safeguarding, or to ask for their instructions every time I go out on holiday,” said one incensed user, from the border district of Tacheng, on the Weibo microblogging website.

The blogger added: “If citizens cannot enjoy even basic rights, how can we live? Would the government please give me a sensible reason for this?”

A second blogger wrote: “Xinjiang is becoming stranger and stranger, regressing as time goes on.”

In June, local state-run media reported that the mostly Kazakh residents of a Xinjiang border district had to give police DNA samples, fingerprints, voiceprints and a “three-dimensional image” in order to apply for certain travel documents, including passports.

A Xinjiang official told the Global Times that the new policy tightening was intended to maintain social order in the region.

Beijing has regularly accused what it claims are exiled separatist groups, such as the East Turkestan Islamic Movement, of being behind attacks in Xinjiang, which has seen a wave of deadly unrest.

But many independent experts doubt the strength of overseas Uygur groups and their links to global terrorism, with some saying China exaggerates the threat to justify tough security measures in the resource-rich region.