A man identifying himself as Uighur poet and musician Abdurehim Heyit is seen in this still image taken from a video posted online by China Radio International's Turkish-language service on Sunday. The video followed claims Heyit had died in a Chinese detention camp. (CRI/Reuters)

THE STRANGE case of the Uighur musician and poet Abdurehim Heyit reveals a lot about China’s incarceration and attempt to brainwash 1 million or more minority Muslim Uighurs in Xinjiang province. Mr. Heyit, a master of the two-stringed dutar, was reported by Turkey to have died in one of the camps China built for the Uighurs. Denying that he was dead, China released a video of Mr. Heyit saying he was in “good health,” but the video could not be verified as genuine, and the uncertainty over his fate raises anew the disturbing question of what is going on in the concentration camps that China has tried to hide from the world.

China has sought for years to assimilate the Muslim Uighur population into the majority Han Chinese, partially by flooding Xinjiang province with migrants from elsewhere. But the effort to crush the population has picked up speed under President Xi Jinping, whose government set up an archipelago of bleak outposts for carrying out forced indoctrination, to eradicate the Uighur language, traditions and culture. At first, China denied these camps existed; then China admitted that they exist but claimed they are for “re-education” and vocational training. As eyewitnesses have verified, the real purpose is much darker, to coerce the detainees to give up their language and culture. Experts have said more than 1 million Uighurs are now detained, out of a population of more than 11 million. Dolkun Isa, president of the World Uighur Congress, told us there may be 2 million or more imprisoned, based on word leaking out to Uighur families and those who have been released.

Other nations, fearful of Chinese bullying and eager to preserve economic ties, have been slow to condemn or even acknowledge this ongoing crime against humanity. But on Saturday, the government of Turkey, a large Muslim state with a significant Uighur population, denounced China’s practices as “violating the fundamental human rights” of the Uighur population in Xinjiang and called the concentration camps “a great shame for humanity.” Other governments also should speak out against this cultural genocide.

Mr. Isa is among those Uighurs abroad who also have paid a terrible price. His communications with his family were cut off 22 months ago, and his mother died without a farewell. His two brothers disappeared into the black hole of detention; one of them is a professor, among the 338 Uighur intellectuals whose detention has been documented. (The true number is undoubtedly higher.) Mr. Isa told us of worrisome reports that Uighur detainees are now being moved out of Xinjiang to prisons elsewhere in China, clouding their fate even further. China must be held to account for crimes against the Uighur population. Worthy legislation is pending in Congress to address this, and the time has come for the rest of the world to demand admission to the camps, in search of a lost Uighur musician and more than 1 million others.