Singapore has disconnected computers from the internet at public health care centers to prevent cyberattacks of the kind that caused its worst breach of personal data, a government official said on Tuesday.

Singapore started to cut web access for civil servants in 2016 to guard against cyberattacks, but stopped short of including public health care institutions. Officials may still surf the web using separate personal or agency-issued devices.

In the most recent attack in June, hackers stole particulars of more than 1.5 million patients, including the prime minister's drug prescriptions, in what the government has called "a deliberate, targeted and well-planned cyberattack."