SINGAPORE - DBS' digital banking services resumed on Thursday (Nov 25) after a disruption that prevented customers from accessing services through its website and app for about two days.

The outage was not caused by a cyber attack, said the bank.

In an update posted on Facebook at 9pm on Thursday, DBS said customer log-ins and transaction activities had returned to normal pre-disruption levels since Thursday morning, though some customers were still facing issues.

"Our digital banking services have returned to normal. Please be assured that DBS' systems remain secure and were not a target of a cyber attack," the bank said.

"For customers who are unable to log in or perform selected transactions, restarting your devices resolves the issue in some instances. Customers using Internet banking are advised to clear their browser cache before logging in again."

The outage did not significantly impact businesses here. Several companies The Straits Times spoke to said there has been minimal disruption to their services.

A Great Eastern (GE) spokesman said: "We have not seen any impact on existing Giro arrangements, payment processing or insurance payouts to policyholders via direct crediting or PayNow to their linked bank accounts."

The spokesman added that GE will advise customers about alternative payment modes and extend grace periods for premium payments where necessary.

"So far, we have only received an enquiry from one customer on this, and we are assisting accordingly," the spokesman added.

Ms Lee Tsui Lin, Prudential Singapore's head of operations, said the insurer provides customers with multiple options for premium payments.

"If any payment service is unavailable, they can tap other options.

"We also have a grace period for premium payments to ensure that customers have sufficient time to complete their payments in such scenarios," she added.

Mr Roy Kee, managing director of cleaning products manufacturer JRW International, said the disruption was not keenly felt as the company still uses cheques for some payments, and also banks with other lenders besides DBS.

"As a new convert to e-banking, this will shake my confidence a bit. The bank could have also communicated with clients better by sending us SMS messages about the disruption," he added.

DBS has seen disruptions to its website and mobile app services from Tuesday morning.

In a Facebook post at 10.35pm on Wednesday, the bank said services were returning to normal and added that it was monitoring the situation closely to ensure they run smoothly.

Although customers said they could log in to its digibank online platforms on Thursday morning, many still could not make transactions or view past ones.

The bank urged customers to restart their devices and log in again.

After restarting her phone, Ms Allison Teo said she could log into the DBS digibank app around Thursday noon to transfer money to a friend via PayNow.

"It was just a small amount as she had helped to purchase a gift for a friend who was discharged from hospital. It wasn't really urgent but I don't like to delay payment," said Ms Teo, 42, a programme executive.

Reacting to the bank's worst outage in more than a decade, the Monetary Authority of Singapore (MAS) said on Wednesday evening that it would consider taking "supervisory action".

"This is a serious disruption and MAS expects DBS to conduct a thorough investigation to identify the root causes and implement the necessary remedial measures," said Mr Marcus Lim, MAS' assistant managing director of banking and insurance.

"MAS will consider appropriate supervisory actions following the investigation. MAS expects all financial institutions to have systems and processes to ensure the consistent availability of financial services to their customers," he added.

Under the central bank's regulations, financial institutions must ensure that the total unscheduled downtime for critical systems affecting services for customers does not exceed four hours within any 12-month period.

Banks must also inform MAS of any incidents affecting critical systems within an hour.

In a Facebook video post on Wednesday, DBS country manager for Singapore Shee Tse Koon apologised to affected customers for causing them inconvenience and blamed faulty access control servers for the outage.

He did not elaborate on details of the server fault.

Access control servers are part of a bank's security system. They handle both login and payment verification using means such as biometrics, authentication tokens and one-time passwords.

The disruption, which was first reported at around 10am on Tuesday, is the worst DBS has seen since 2010, when a major systems failure took down all consumer and business banking services at the bank.

Customers were unable to withdraw cash from ATMs or make point-of-sale payments for about seven hours.

DBS shares slid 0.83 per cent to $32.11 on Thursday.