As reports of the forced detention and brainwashing of up to one million ethnic Uighurs continue to emerge from China's Xinjiang autonomous region, the ABC has heard a rare account from a witness who has been inside a camp.

Tarim, whose second name we have withheld, bribed his way into one of the "training" centres reserved for the Muslim minority, to see his sister, who was detained in 2016.

She is being held in the facility outside Aksu City, in western Xinjiang (also known as Turkistan), which Tarim described as a "concentration camp".

"It was April and there was snow in some parts, and I saw about 500 persons on the concrete, on the ground," he told PM in his native language, through a translator in Sydney.

"And also there were about 700 or so people … in the queue to get food, and at the same time they were singing patriotic songs: I love Communist Party, I love Xi Jinping."

Testimony from an Uighur eyewitness. ( Supplied )

Tarim, who fled to Turkey to avoid arrest after his visit, said his sister was crying, had lost weight, and was too afraid to speak freely.

"I asked her how she was, and she said, 'good', but I could feel that she was in fear from her face, and she was actually shaking and she was looking around," he said.

"She said they were attending classes, but from her situation, it was clear that she was in a state of fear."

Tarim estimated there were thousands of Uighurs in Aksu City's facility alone, separated into male and female quarters.

China denies it is holding people in concentration camps and claims it is taking security measures to fight terrorism in Xinjiang, where tensions between the Han Chinese and the Muslim Uighurs have run high for more than a century.

But Tarim rejects China's explanations.

"The concentration camps are not just designed to eliminate Uighur culture and language.

"It is actually designed to exterminate — eliminate — the whole Uighur nation as people," he said.

"People are talking about 1 million in concentration camps, but in my estimate, it is about 5 million people who are taken into camps."

The figures are impossible to verify.

The next generation

The eyewitness report comes as concerns mount about the way the Chinese Government is dealing with Uighur children.

Dozens of orphanages have been set up in Xinjiang in recent months, in an alleged effort by Beijing to systematically distance young Muslims from their families and culture.

Children are being removed even when their families are willing to care for them, according to Financial Times Beijing correspondent, Emily Feng.

"I've interviewed a number of people who had relatives who very much wanted to take care of children whose parents had been detained, but the children were forcibly taken away from them and sent to state orphanages," she told PM.

Ms Feng said this was part of a broader campaign by the Chinese Government to eliminate Uighur identity.

"If your theory is that the Chinese Government is trying to stamp out Uighur identity and Uighur culture, then it makes perfect sense to go after the next generation of Uighur children in detaining them along with their parents," she argued.

"The worry among Uighur exiles that I've talked to is this very real fear that their children will grow up not recognising the people that they came from."

China denies it is holding people in concentration camps and claims it is taking security measures to fight terrorism in Xinjiang. ( Reuters: Petar Kujundzic )

"We're looking at potentially hundreds of thousands, if not millions, of children that have already been affected, and there is no telling what numbers might be going forward."

Shirmuhammad Hasan, who is from Xinjiang but now lives in Australia, fears his two year-old son Ihsan has been sent to one of the orphanages.

He has not received any news about the child since his wife was sent to a re-education camp earlier this year.

"I have no idea what's happened with my son," Mr Hasan said.

"I'm really worried about him and what's happening to him. I can't call anyone except my mother, and she can't go to the north part of East Turkistan because it's not safe."

Mr Hasan said he would like to return to Xinjiang to look for his son, but he was concerned he would not be able to leave China if he did.

"It's too dangerous to go back," he said.

"I would get arrested at the airport and I'll be gone forever."

The communication blackout

Many Uighurs living in Australia say even communicating with their family members in China puts relatives at risk.

"At this stage there is a communication blackout," Mamtimin Ala, president of the Australian Uighur Association said.

"The Chinese Government has cut off any kind of communication lines with our family members there.

"We are in the grip of anxiety over the wellbeing of our family members.

"This is huge psychological pressure on us by the Chinese Government, that we have no idea about what's going on there."

Mr Hasan said many Uighur people in China were now afraid of contacting relatives outside the country for fear of Chinese authorities.

"I used to chat with my ex-wife on Wechat, but since I've been living in Australia, the police in East Turkistan have started checking people's telephones on the street," he said.

"If they see something they don't like, or that you're communicating with someone overseas, they'll take you to prison."

Mr Hasan lost contact with his wife earlier this year before she was sent to one of the re-education camps.

"She just deleted me all of a sudden. She said 'I'm having trouble here' and just deleted me."

Some Uighurs believe the Chinese Government is attempting to exert pressure on them even though they now live in Australia.

Nurmuhammed Turkistani, president of the East Turkistan Australian Association, claims Uighurs are being directly contacted by people claiming to be from the Chinese consulate.

"I have received phone calls from the community members a number of times," he said.

"More than 20 times that they were contacted by so-called Chinese consulate officers and also they were urged to contact the Chinese consulate in relation to the matter, otherwise they will be facing consequences."

The Chinese embassy did not respond to the ABC's request for comment.

In the past, it has said some calls purporting to come from the embassy were from scammers.

But Mr Turkistani said he believed the calls were part of a broader strategy to intimidate Uighur people in Australia, and stop them speaking out.

"We believe that the Chinese embassy is threatening to the community members, causing psychological fears and also harassment to their family members in our region," he said.

The Australian Government has expressed concern over how Uighur people are being treated in China.

But Dr Ala is urging the Government to follow the lead of the United States and consider sanctions against senior Chinese officials linked to human rights abuses.

"A fundamental question is whether or not we should do business with a country which is committing crimes against humanity," he said.

"This is also quite a crucial moral test for the Australian Government.

"If the Australian Government is silent over this matter, China's Government will put more pressure on Australia to be silent over many other matters not necessarily happening to Uighurs, but also happening to Australians in the future."

Tarim sent a similar message.

"I am asking from the free world, as well as from the Australian Government, is to help prevent the extermination of the Uighur nation by the Chinese Government."