Prisoners in China are regularly transported wearing blindfolds. It is unclear whether the men are being held for criminal offenses or for other reasons. The YouTube account which uploaded the video described it as demonstrating the "long-term suppression of human rights and fundamental freedoms by the Chinese government in the Xinjiang Uygur Autonomous Region."

Evidence points to Xinjiang

A western intelligence official told CNN they believed the video was authentic.

"China needs to be challenged for this behavior," the official said. "So many countries support China on human rights without understanding that it appears to be attempting to wipe out the entire Uyghur identity."

Ruser said that information in the video itself -- including data from the drone camera and visible landmarks that could be compared to open source satellite photos -- indicated that it had been recorded in Kuresi Station, near the city of Korla in central Xinjiang.

He added that the men in the video appeared to be being transported from a detention center in Kashgar "to the much more expansive Korla facilities."

A US official also told reporters on September 24 that Washington believes the video to be authentic. "Let's not talk about the validity of any particular evidence. It's the summary evidence, it's the bulk of evidence," State Department official David Stilwell said.

Hua called Pompeo's statement "utterly defamatory and groundless," adding that Beijing urged relevant US officials to face the facts, be objective and fair, and not adopt double standards on counter-terrorism, let alone to use this as an excuse to launch unwarranted attacks against China," referring to Beijing's claims that activities in Xinjiang are about stemming a terrorist threat in the region.

'That used to be me'

For two former detainees in Xinjiang, the video was strikingly familiar.

Amanzhan Seiit, a Muslim ethnic Kazakh, said he was detained in China in 2018, but was never told what for. After several weeks in one camp, he said he was moved to another in a fashion exactly the same as shown in the video.

"We were made to sit just like that," he told CNN. "They put cuffs on our hands and legs and masks over our heads. Lots of police were there with guns."

He was released after several months and now lives in Kazakhstan, a country on China's western border. While detained, he says the fear of not knowing what might happen was the worst.

"Watching the video, I'm still scared because I know what the prisoners are thinking," Seiit said. "They don't know where they're being taken or if they'll be shot dead. It's terrifying."

There are no publicly known instances of shooting deaths inside the camps. More than 3,000 miles away, Omerbek Bikali, another Muslim Kazakh, knows how it feels to be scared in custody.

He lives in the Netherlands now, after being detained in a Chinese camp for months in 2017. He claims he was tortured regularly and describes the camps as hell.

"I think the reason they want to torture us is, firstly, to make us physically weak so that you cannot resist," he said.

Bikali said though he was transferred between camps by car, he too had a bag placed over his head and his hands shackled. Watching the drone video, he was overcome with emotion.

"I feel so sad. That used to be me. I cannot forget that. It's criminal," he said.

Xinjiang authorities and Chinese Foreign Ministry officials did not respond to requests for comment about the former detainees' allegations.

Restricted region

He declined to answer a question as to how many people remained in the camps.

Zakir said the camps had taught Uyghurs to practice their religion "normally" but added no single religion or minority group had been targeted.

"If there still skeptics, whether they are journalists, officials or religious figures, we welcome them to visit anywhere in Xinjiang or go to any vocational training center of their choice -- anytime," he said.

Previous attempts by CNN to visit the internment camps have been repeatedly blocked by local authorities.