In September, China's industry and information technology ministry issued a notice on "safeguarding the legitimate rights and interests of citizens online", which laid out rules for enforcing real-name registration.

The notice said telecom operators should use "artificial intelligence and other technical means" to verify people's identities when they take a new phone number.

A China Unicom customer service representative told AFP that the December 1 "portrait matching" requirement means customers registering for a new phone number may have to record themselves turning their head and blinking.

"In next steps, our ministry will continue to...increase supervision and inspection...and strictly promote the management of real-name registration for phone users," said the September notice.