MOSCOW, April 3 (Reuters) – A problem with payment systems sowed chaos on Friday ‌for some Russian shoppers, forcing the ‌turnstiles on the Moscow metro to allow people ​to enter without payment and even forcing a regional zoo to ask visitors to use cash.

The cause of the payment system problem ‌was not immediately ⁠clear but shoppers and retailers said that they experienced problems with ⁠Sberbank, the country’s biggest bank, and with payments with QR codes.

The central bank did ​not reply ​to a request ​for comment. Sberbank ‌said problems had been resolved but gave no details on what caused the problems.

Shops and petrol stations asked customers for cash for about an hour on Friday, citing ‌a problem with payment ​systems, Reuters reporters said.

The Moscow ​metro turnstiles ​let people enter for free ‌at one point, TASS reported. ​A zoo ​in Belgorod said card payment systems were down, and asked visitors to pay ​cash.

Moscow and ‌the surrounding region has a population ​of 22 million people.

(Reporting Elena Fabrichnaya; ​editing by Guy Faulconbridge)