A Uyghur woman has detailed conditions she says were tantamount to torture inside one of China's "re-education camps" in far western Xinjiang province.

Key points: It's rare for Uyghurs to speak out because of fear of retaliation

It's rare for Uyghurs to speak out because of fear of retaliation Gulbahar Jelilova says she was beaten and injected with unknown substances

Gulbahar Jelilova says she was beaten and injected with unknown substances China's Government says camps help re-educate extremists

The UN has cited estimates that up to 1 million ethnic Muslim-minority Uyghurs may be held involuntarily in extralegal detention in Xinjiang.

China's Government says the camps are vocational training centres providing language training and re-education of extremists.

But reports from inside the centres tell a very different story.

Gulbahar Jelilova says she was in a Chinese "concentration camp" for more than a year. ( Supplied )

Gulbahar Jelilova, who says she spent 15 months inside one of the camps, has given a rare firsthand account of the conditions.

"We were kept in dark rooms with rats and mice," she told the ABC's PM program.

"Sometimes they were tying up a weight of 5 kilograms to our feet as a way of punishment.

"If they wanted to punish even heavier, they would put handcuffs [on us] and we would be forced to look at the wall across for about 17 hours."

Ms Jelilova, who is originally from Kazakhstan, has spent the last two decades doing business on the Chinese-Kazakhstani border.

She said in May 2017 she was arrested in the Chinese city of Urumqi on charges of illegal transferring 17,000 yuan ($3,500) between China and Turkey.

"While I was in the camp I told them that I was a foreigner and that I didn't have any wrongdoings," she said.

"We were told we didn't have any rights there. We didn't have any rights to make phone calls outside … we were like dead people."

Satellite images said to show the size and spread of internment camps. ( ABC News/Google Earth/Digital Globe )

Most Uyghurs who have been inside the camps won't speak about their experiences because of fears other family members will be detained in retaliation.

Despite Ms Jelilova's concerns that Chinese police are keeping tabs on her in Turkey where she currently lives, she said she felt compelled to speak out on behalf of other young women currently in detention.

"I cannot eat comfortably when I think about those people. Under those circumstances how can I keep quiet?" she said.

Forced to take unknown medicines

Ms Jelilova outlined how the women were forced to take unknown medication while in the centre.

"While I was in the camp, they used to give us injections, take blood samples, give medications that we didn't know," she said.

"If we asked what medication it was, they would penalise for asking this question.

"And none of the female people were having monthly periods because they were giving us specific medication that was stopping the periods."

Chinese officials call the camps vocational skills education centres. ( Reuters: Thomas Peter )

Ms Jelilova's accounts contradict the Chinese Government but they do match up with reports of other Uyghurs and human rights groups.

She said she was beaten inside the camp and when she first entered she weighed 76 kilograms but within a month had lost more than 20 kilograms.

"The total aim of those concentration camps is to eliminate the Uyghur people, the Muslims," she said.

Ms Jelilova said she was let out of the camp following a sustained lobbying effort by her family.

"I was released from the concentration camps three months ago, but every single day the situation in the concentration camps is in front of my eyes.

"The cries of the people are in my ears."

The ABC has repeatedly sought comment from Chinese officials but has received no response.

China has said Xinjiang faces a serious threat from Islamist militants and separatists who plot attacks and stir up tensions between the mostly Muslim Uyghur minority and the ethnic Han Chinese majority.