Rights activists have criticised the technology -- already in use at dozens of Moscow supermarkets -- as an example of creeping state surveillance

"To enter the metro, passengers do not need a card or a smartphone. They just need to look at the camera on the turnstile," Deputy Moscow Mayor for Transport, Maxim Liksutov, said in a statement.

The official said he expected the system dubbed "Face Pay" to be used by 10 to 15 percent of passengers within the next two to three years.

He added that signing up to the system, which requires a bank account that has metro riders' biometric data on file, is "voluntary".

"Other payment methods aren't going anywhere," Liksutov said.

Authorities expect the facial recognition payment system to speed up traffic in Moscow's sprawling metro network.

They have promised that the data will be securely encrypted with turnstile cameras reading a "biometric key" and not an image of the rider's face.

The authorities are working to expand an initiative to collect Russians' biometric data, which began in 2018.

Earlier this year, the Kommersant business newspaper reported that authorities are hoping to increase the number of people who have signed over their biometric data from around 160,000 to 70 million over the next two years.

Facial recognition has rapidly expanded across Moscow in recent years, with authorities using it as a tool to enforce lockdown measures.