Muslims living in China’s western region of Xinjiang are being forced to put up Communist Party officials in their homes, effectively extending state surveillance into the last place they had felt safe from intrusion.

Since early 2017, the Uighur people have been subjected to an increasingly strict security regime, including armed checkpoints and streets lined with facial recognition-equipped CCTV.

Experts and human rights groups believe around a million mostly male Uighurs are being held in secretive internment camps across the province. After initially denying the camps’ existence, the Chinese government has begun referring to them as voluntary “vocational training centres”.

Now, in interviews with the Associated Press, Uighurs living in exile have described how a state “cultural exchange” programme has thrust government spies into the only private space most Muslims in Xinjiang had left.

According to the ruling Communist Party’s official newspaper, 1.1 million local government officials have been deployed to spend about a week every two months living in the home of an Uighur host family.

The government calls it the “Pair Up and Become Family” campaign, with social media posts by the Uighurs involved referring to the officials as their new “relatives”.

“Look, I have a Han Chinese mother now!” reads the caption of one picture posted online by the 39-year-old sister of Halmurat Idris, an Uighur Muslim living in Istanbul. Han Chinese make up about 90 per cent of the country’s ethnic mix, with Uighurs numbering between 1 and 3 per cent.

The government describes the programme as voluntary, but China’s Muslims are well aware that refusing any state initiative can lead to being branded a potential extremist. Social media images show the new “relatives” attending Uighur weddings, funerals and other occasions once considered intimate and private.

Mr Idris said that seeing the picture of his sister alongside an elderly woman he did not know, her face fixed with a mirthless smile, made him feel sick.

“I wanted to throw up,” the 49-year-old said. “The moment I saw the old woman, I thought, ‘Ugh, this person is our enemy.’ If your enemy became your mother, think about it – how would you feel?”

AP said it had interviewed four other Uighurs living abroad who had been in contact with relatives back home in Xinjiang, and who described their loved ones as constantly on edge in their own homes, knowing that any misstep – a misplaced Quran, a careless word – could lead to detention or worse.

In the presence of their faux relatives, the interviewees’ family members could not pray or wear religious clothing, and the government officials were privy to their every move.

Meanwhile, a new analysis of satellite images by experts and Reuters has revealed the growing extent of 39 detention camps for Uighurs across Xinjiang province.

Collectively, the facilities have almost tripled in size in the 17 months between April 2017 and August 2018, while the most recent imagery suggested construction work was still going on at many of them.

Though covering an area roughly the size of 140 football pitches, the camps represent just a portion of the total number of detention facilities that are believed to exist in the state. Access for journalists to the province is tightly controlled, making it almost impossible to verify the precise number and nature of the camps.

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China refers to its broader crackdown on Xinjiang as the “people’s war on terror”, which started in 2014 after a series of violent attacks that authorities blamed on extremists. Beijing said in August that “those deceived by religious extremism... shall be assisted by resettlement and re-education”.

That admission came after the UN’s Committee on the Elimination of Racial Discrimination said it was “alarmed” by reports from the province, criticising the “broad definition of terrorism and vague references to extremism and unclear definition of separatism in Chinese legislation”.

Members of the committee said there were credible reports that the Chinese government had “turned the Uighur autonomous region into something that resembles a massive internment camp”.