SINGAPORE - DBS Bank said all of its banking services had resumed on Sunday (Oct 15) morning, after more than 12 hours of disruption that began on Saturday afternoon.

In an update on Facebook on Sunday morning, the bank said all its services had returned to normal, including PayLah and digital banking services.

"However, any customer who may still experience difficulties logging in to their accounts via their mobile app can try to log in with digibank online/Internet banking using SMS OTP," said the update.

"We are also aware that some of our customers' PayNow/Fast transactions were interrupted when the disruption happened, and will be processing these with utmost priority."

The bank added that customers will be updated on the status of their transactions when processing is completed.

Citibank said in a Facebook post at about 7pm on Saturday that its mobile app and Internet banking services were down.

At around 10am on Sunday, Citibank said in a Facebook post that its mobile app and Internet banking services had "resumed overnight".

However, some users saw a notification on the Citibank app on Sunday morning, informing them of a scheduled maintenance between 12am to 12pm on Sunday.

The notification stated that during the maintenance, customers would not be able to log in to the Citibank app, use Internet Banking, or make online purchases using one-time passwords.

Issues with the service of both banks began to surface on Saturday afternoon.

The Downdetector website, which tracks service disruptions, had 3,800 people reporting issues with DBS' services at about 4.10pm, and 279 complaints about Citibank's services at about 4.40pm.

In a Facebook post at about 6.10pm on Saturday, DBS said its investigations showed that the service disruption was caused by an issue at a data centre, which is also being used by other organisations.

On Saturday evening, US data centre operator Equinix told The Straits Times it was aware that a technical issue at one of its data centres impacted some customers' operations, including DBS, and it is investigating.

In an update on Sunday morning, an Equinix spokesman said the technical issue that occurred on Saturday raised the temperature in the data centre, which impacted some customers' operations.

"We are conducting a thorough investigation into this event to identify ways we can better meet our customers' needs," said the spokesman. "We will further communicate with our customers as more detail becomes available."

On Saturday, netizens complained on the HardwareZone forum and commented on the DBS/POSB post on Facebook about being unable to access the bank's app and website or use their cards to make payments in stores.

DBS customers were also reportedly unable to use the bank's ATMs in Toa Payoh, Bishan and Sengkang.

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This article was first published in The Straits Times. Permission required for reproduction.