They even threatened to shoot them if they resisted.

"We took (them) all forcibly overnight," the former Chinese cop told CNN.

"If there were hundreds of people in one county in this area, then you had to arrest these hundreds of people," he said.

In a three-hour interview with CNN, conducted in Europe where he is now in exile, Jiang, the name by which the cop wanted to be called, revealed rare details on what he described as a systematic campaign of torture against ethnic Uyghurs in the region's detention camp system.

"Kick them, beat them (until they're) bruised and swollen," Jiang said, recalling how he and his colleagues used to interrogate detainees in police detention centers. "Until they kneel on the floor crying."

During his time in Xinjiang, Jiang said every new detainee was beaten during the interrogation process -- including men, women and children as young as 14.

Who are Uyghur Muslims?

Uyghur Muslims are a Turkic minority ethnic group originating from and culturally affiliated with the general region of Central and East Asia.

It is now widely publicized that their human rights are being crushed by China and they were sent to "re-education camps" by the communist regime in Beijing.

The Uyghurs are recognized as native to the Xinjiang Uyghur Autonomous Region of the People's Republic of China.