HSBC, Hong Kong’s biggest bank with a customer base of 6.2 million, suffered a system breakdown on Friday afternoon.

The bank’s mobile banking app could not be accessed, instead showing a message stating the system was under maintenance and would be available at a later time.

A staff member at the bank’s Mong Kok branch said HSBC’s computer network across the city had failed, but did not know the reason for the stoppage.

An HSBC spokesperson said: “Our banking services are gradually returning to normal. We apologise for any inconvenience caused.”

PayMe, HSBC’s peer-to-peer transfer app, appeared to function normally during the shutdown, as did the mobile apps of HSBC subsidiary Hang Seng Bank.

“The incident is an alert, not just to HSBC but also to other lenders, as they all now promote digital banking. It is important for HSBC and other banks to invest in the security of their systems to ensure customers’ services are not interrupted,” said Kenny Ng Lai-yin, a strategist at Everbright Securities International.