DBS said in a post on Facebook that its services had now returned to normal and that it continues to monitor the situation.

"We appreciate your patience and are sorry for the inconvenience caused," the lender, which is also Southeast Asia's largest said.

DBS faced a two-day disruption to its digital banking services in late 2021, which prompted the Monetary Authority of Singapore (MAS) to impose an additional capital requirement of about $692 million on the bank in February last year.

In a statement late on Wednesday, MAS said the disruption of DBS' digital services was "unacceptable", and demanded that the lender conduct a "thorough investigation".

"MAS will take the commensurate supervisory actions against DBS after gathering the necessary facts," it said, without providing any further details.

DBS shares ended slightly lower at S$33.59 per share on Thursday.

(Reporting by Yantoultra Ngui in Singapore and Kanjyik Ghosh in Bengaluru; Editing by Christina Fincher and Sharon Singleton)