The data was obtained by a hacker through a third-party service provider, Fuji Xerox, which the bank employs to print its private clients' bank statements, according to a statement issued jointly by the bank and Fuji on Friday evening.
It was not immediately clear how long the bank, Fuji Xerox or the police have known about the theft.
Market observers said the theft would be viewed with some concern by Standard Chartered's Asian private banking clients, for whom confidentiality is often a priority.
Standard Chartered chief executive Ray Ferguson stressed that the confidentiality and privacy of the bank's clients were "of paramount importance to us", and that the bank was taking the incident "very seriously".
"Customer data protection is our responsibility, and we sincerely apologise to all our customers and specifically, to our private bank clients who have been affected,” he added.
Standard Chartered said it had found no evidence of any unauthorised transactions resulting from the client data theft, but that, as a a "precautionary measure", it was contacting all of those clients whose data had been compromised.
Fuji Xerox said it was the first time in the company's history in Singapore that such an incident had occurred, and that it had taken "all appropriate action" to protect the integrity of our server systems.
Bert Wong, chief executive of Fuji Xerox, said the theft occurred as a result of "unauthorised access by a third party" to a particular server used by Fuji Xerox for its Standard Chartered Private Bank work.
The matter is now being investigated by the police and the Monetary Authority of Singapore. In a statement on its website, the MAS said it would review the investigation report into the theft before considering whether regulatory action against the bank would be called for.
The theft of the Standard Chartered client data, the MAS added, underscored the need for greater vigilance on the part of financial institutions with respect to the security of their IT systems and customer information.
Standard Chartered Private Bank is the private banking division of the UK-based, Asia-focused Standard Chartered banking group. It was launched there in 2007.
