Online banking services and ATMs provided by HSBC and its subsidiary Hang Seng Bank broke down for several hours on Sunday, leaving millions of customers in Hong Kong unable to access their accounts.

Account holders with the city’s largest bank complained that its online banking app was out of service, while several others said they could not withdraw money from HSBC’s ATMs at about 11.30am.

Several Hang Seng customers had said they were also unable to access online banking services, with a message appearing on the screen stating: “We are not able to process your instruction.”