In China's Xinjiang province, the predominantly Muslim Uighur minority have nowhere to hide.

Facial recognition software reportedly alerts the authorities if targeted individuals stray more than 300m from their homes and workplaces. Residents face arrest if they fail to download smartphone software that allows them to be tracked, according to social media users.

Simply wishing to travel outside China can be cause for arrest. At least 120,000 Uighurs have been imprisoned in "re-education camps" in the last two years, said the US government-funded Radio Free Asia.

Others put the number as high as one million, which a group of US Congress members last month called the largest current mass incarceration of a minority population anywhere.

China has refused to comment on reports of mass detention. And it denies repression of the Turkic-speaking Uighurs, some of whom have been engaged in a low-level separatist movement for years.

Beijing said it faces Islamist insurgency in Xinjiang, and blames Uighur militants for a number of attacks across the country. It has labelled a group of Uighur leaders as terrorists.

Outside experts agree China faces a threat. Hundreds of Uighurs were reported to have fought for Islamic State in Iraq and Syria, some vowing to return to spill Chinese blood "in rivers".

Still, what is happening in Xinjiang appears beyond any reasonable response to the danger.

Indeed, it looks much more like a deliberate testbed for techniques that, some human rights specialists worry, could become a model for elsewhere.

China has become notably more repressive since the rise of President Xi Jinping.

Anti-corruption drives have seen hundreds of Mr Xi's political foes arrested, while the government has raised its investment in cutting-edge surveillance technology.

Beijing has become ever more open to using its growing political clout to intimidate opponents and stymie criticism.

No group has felt this more than China's estimated 11 to 15 million Uighurs.

As early as 2015, Chinese officials were using a range of techniques to intimidate and infiltrate Uighur communities overseas, threatening individuals that their families at home would suffer if they did not help Beijing gather information on Uighurs they consider hostile.

Last year, China began a worldwide campaign to persuade countries to deport Uighur students, with dozens sent home from Egypt alone.

Within Xinjiang, Beijing has created what experts say appears the most comprehensive system of high-tech state surveillance on the planet.

A Metro system opening this year will require passengers to show their ID for every ride, while residents were last year ordered to turn in all electronic devices for official checks for "terrorist videos" and other illicit content.

Beyond the periodic US reports and activity by pro-Uighur groups and media outlets, the world shows little interest in events in Xinjiang.

For Washington, the treatment of the Uighurs does not compete with issues such as trade and North Korea.

European states, desperate for trade with Beijing, have shown even less appetite to criticise Mr Xi's administration.

China's Uighurs now have little chance that those outside the country will support them.

The Gulf States and Turkey, which might have once seemed a potential source of support, appear ever less interested.

If this kind of suppression of minorities and dissent becomes widespread in years to come, we may regret not paying more attention. - REUTERS

The writer is Reuters global affairs columnist.