Those targeted visited clinics between 1 May 2015 and 4 July of this year.
Data taken include names and addresses but not medical records, other than medicines dispensed in some cases.
“Information on the outpatient dispensed medicines of about 160,000 of these patients” was taken, the statement says.
“The records were not tampered with, ie no records were amended or deleted. No other patient records, such as diagnosis, test results or doctors’ notes, were breached. We have not found evidence of a similar breach in the other public healthcare IT systems.”
The data of Prime Minister Lee Hsien Loong, including information on his outpatient dispensed medicines, was “specifically and repeatedly targeted”. Mr Lee has survived cancer twice.
Singapore, a wealthy city state, prides itself on its stability and security.