In a statement, OCBC says that at around 9.00am local time its IT team discovered that the core banking system could not properly connect to various front-ends. The problem was fixed by 1.00pm, says CEO David Conner, who also moved to reassure customers that all their data was protected during the outage.

Throughout the morning, OCBC moved to keep users up to date by posting messages on its Web site, ATMs and branches as well as on Twitter, learning lessons from its rival DBS, which recently admitted communications failings about its outage last year.

The Monetary Authority of Singapore told DBS to set aside $230 million additional regulatory capital for operational risk and told it to improve customer communications procedures following the issue. It will assess OCBC's compliance with risk management rules before deciding what action to take against it.