Ethnic Uighurs have launched a global campaign to press China for video proof that their missing relatives are alive, turning the tables on Beijing's use of video to counter claims that a renowned Uighur had died in custody.

The social media campaign was launched on Tuesday under the hashtag #MeTooUyghur after China released a video showing a man who identified himself as Uighur poet and musician Abdurehim Heyit and saying he was alive and well.

The video was made public after Turkey claimed that Heyit had died in a Chinese prison in a statement in which Ankara condemned China for herding vast numbers of Muslim minority Uighurs into “re-education” camps in the remote Xinjiang region.

“Chinese authorities showed video as proof Heyit is still alive. Now, we want to know, where are millions of Uyghurs?” said Murat Harri Uyghur, an activist in Finland, who created the hashtag.

He told AFP that his own parents had been detained previously but were released last year. The hashtag has prompted posts from Uighurs around the world with pictures of missing mothers, fathers, sons, daughters or friends, and demanding to know their fate.

A UN panel of experts has said that nearly one million Uighurs and other Turkic-speaking minorities are being held in extrajudicial detention in camps in Xinjiang, where most of China's more than 10 million Uighurs live.

Beijing at first denied the allegation, but later said it has put people into “vocational education centres”.

Many overseas Uighurs have not been able to contact relatives and friends in China for years as phone calls and messaging platforms are under close Chinese surveillance, said Rushan Abbas, a US-based rights activist.

She is demanding authorities release a video of her sister, a physician, who she says was “sent for vocational training”. China has cracked down hard in recent years to squelch persistent violent unrest in Xinjiang.

Many Uighurs have long accused Beijing of seeking to extinguish their culture to neutralise what Beijing considers a “terrorist” threat in Xinjiang, and critics say Uighurs in the camps are being brainwashed to conform with Chinese society and abandon Islam.

Arslan Hidayat, son-in-law of prominent Uighur comedian Adil Mijit, posted a Facebook video saying his father-in-law was missing and calling for a “proof of life video” of Mijit and others “who have been locked up in Chinese concentration camps”.

Turkey on Saturday released perhaps the strongest statement by a Muslim country yet over the camps, calling Beijing's treatment of Uighurs “a great cause of shame for humanity”.

It also said it had learned that Heyit had died while serving an eight-year prison sentence “over one of his songs”.

On Monday, China's foreign ministry called the Turkish statement “vile” and urged Ankara to withdraw its “false accusations”.

The Muslim world has so far been conspicuously quiet on the Uighur issue, possibly to avoid Chinese diplomatic or economic retaliation.