China's mass surveillance strategy moved up a step on Sunday as new mobile phone users were told to undergo face scans to help prove their identities.

The Agence France-Presse news agency cited a source from the state-owned telecoms giant China Unicom as saying the "portrait matching" requirement would mean that people registering a new phone number would have to record themselves turning their head and blinking.

The new rule was announced by the Ministry of Industry and Information Technology in September to safeguard "the legitimate rights and interests of citizens online."

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Additional security check

Mobile customers are already required to show a form of identification when signing up for new phone contracts, but the face scans will now be used to verify the person is a genuine match to their ID.

Some social media users voiced concerns their biometric data could be leaked or sold.

"This is a bit too much," wrote one user on Twitter-like Weibo, commenting under an article about the new rules.

"Control, and then more control," posted another, according to AFP.

China has tried for years to match internet users with their real identities to prevent online fraud and monitor political posts. Social media firms were forced to roll out real-name registration almost a decade ago.

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Citizen-tracking stepped up

While Beijing insists the latest measure will boost cybersecurity and cut internet fraud, privacy groups see face scans as another example of China's leaders trying to track their citizens.

Facial recognition is already widely used in China, with Beijing aiming to install 400 million new surveillance cameras by 2020. The cameras are currently used to identify jaywalkers, monitor workers' attendance and screen people entering residential and government buildings.

The new face scan policy coincides with the rise of artificial intelligence and the rollout of Beijing's new social credit system, under which each citizen is scored according to their behavior. Similar private blacklisting databases have also been set up.

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Legal challenges

Last month, growing suspicion about facial recognition prompted one of China's first lawsuits over the issue.

A Chinese professor filed a claim against a safari park in Hangzhou, eastern Zhejiang province, for requiring face scans for entry, according to the local court.

The law professor reportedly said the change from a fingerprint entry system was an infringement of his consumer rights.

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