The young boy, who would have been the same age as my son when he last saw his mother, sat silent and still.

The four-year-old had recently arrived in Australia with his father and three-year old sister from Xinjiang in China. They separated from their mother: they suspect she's in a Chinese camp (in code, she told them she "had malaria" before they lost touch).

Speaking through an interpreter in Adelaide, his father explains:

"Suddenly contact was lost. The children started asking, 'Where's my mum? Where's my mum?'.

"I said, 'one month, maybe she's coming after one month'. But they get used to the situation. They don't talk.

"He plays a game, pretends to be driving a plane saying, 'I'm coming Mum'." ( Unsplash: Chris Leipelt )

"Look at this child. He's not talking. The little girl is always crying during the night, she refuses to eat. I have to tell them, your mum has been kept by Chinese authorities.

"Little child, what can he understand? He says, 'alright, I'll become old and learn to drive a plane to get my mum back'. At home, he plays a game, pretends to be driving a plane saying, 'I'm coming Mum'.

Their story was the most disturbing Louisa Lim and I heard on our mission to talk to Uighurs in Australia.

According to a United Nations panel on racial discrimination, there is credible evidence that a million or more Uighurs, a Turkic ethnic group in north-west China, are currently detained in prison or "re-education camps".

The Chinese Government flatly denies the existence of these camps, but satellite images and security company propaganda tell a different story.

And so do the Uighurs who have moved to Australia. We spent six months trying to find Uighurs here able to bear witness to the assault on their language, religion and culture. But fear for their friends and relatives in Xinjiang (East Turkestan as Uighurs know it), prevented those in Sydney or Melbourne from going on the record.

"You'll need to find someone with nothing left to lose," one suggested.

'There's surveillance every 100 metres'

The largest Uighur community in Australia is in Adelaide, largely in the flat northern suburb of Gilles Plains. Last month, when we visited, family after family came forward to tell their stories.

They had one common message: being a Uighur is a crime.

Dolkin's Ablat's father and three of his brothers, who have all been taken away to the camps. ( Supplied )

Meyassar and Dolkin Ablat compiled a list of all their relatives and friends in Dorbiljin (Emin County), and estimated that 90 per cent of the men between the ages of 15 and 50 were taken. Even Dolkin's diabetic father, who had worked for the local government for 40 years, was taken away.

Meyassar, who has been in Australia since 1985, related a first-hand account.

"There's surveillance every 50 to 100 metres. Your phone gets checked, you get body-searched, the women are not allowed to wear scarves, you're not allowed to enter mosques; you're not allowed to fast," she said.

"Everything is monitored. This person I spoke to had someone from the government staying in their home."

Dorbiljin's most famous son, the 19-year old international footballer Irfan, who played for China's U19 national team and scored one of the most spectacular goals ever seen in China, was taken away for "visiting foreign countries".

Even party members are at risk

The first camps, which opened in 2013, targeted Uighurs with religious leanings or overseas connections. Now even those who have loyally served the Chinese Communist Party are incarcerated.

This became clear when we talked to a confident young Uighur man. His father had been a deputy party secretary (the highest rank open to Uighurs) in Karamay, a wealthy Han Chinese town in Northern Xinjiang.

Both his parents had served in the army, and his mother had been a police officer for more than 30 years.

He's incredulous at their disappearance, having grown up "under the red flag".

"Doctors, scientists, even pop singers are missing," he said.

"For the Chinese Government, you don't have to commit some kind of crime. You're Uighur? That reason is more than enough for them to come and put you in these re-education camps … My father, he's not religious at all. I don't remember even once he was praying in his life."

Abdulsalam Alim has been in Australia since 1999. All the other adults in his family bar one are in camps or in prison. ( Supplied )

Life outside the camps

Life outside the camps is also repressive, and surveillance of the population varies from the high-tech, to old-fashioned Maoist methods.

For families from southern Xinjiang who openly practise Islam, the situation has been grim for some time.

Abdulsalam Alim, a community leader who has been in Australia since 1999, brought a list of names of his immediate family in Khotan.

All the adults — except one female cousin who had been left with nine children to care for — were either in camps or in prison. He was told that two of the children, whose parents had been detained, were sent to a boarding school near Shanghai. They have lost contact with the children, who have effectively been orphaned by the state.

Abdulsalam's last contact with his elderly mother was early June, in the form of a stilted, two-minute conversation they both knew was monitored.

Surveillance reaches so deep, it changes how a mother greets her son.

Abdulsalam greeted her with the phrase "Salam Alaikum" (peace be upon you), universal across the Islamic world, but it is forbidden in China. His mother was obliged to reply with the Uighur equivalent of "hi". Before she could talk to her grandchildren, the awkward call was over. Now she cannot be reached. The number is "restricted".

A disturbing feature of all accounts is that while Uighurs are taken into camps in ever-greater numbers, no-one is coming out.

Graeme Smith is a fellow in the College of Asia and the Pacific at the Australian National University. He co-hosts the Little Red Podcast with Louisa Lim, and this article is based on this month's episode.