“Are we happy? I don’t think so, because it will slow us down in terms of day-to-day productivity. In terms of security, safety of our systems, safety of our citizens and information concerning them, it’s absolutely necessary,” he told Singapore media during a visit to Myanmar.
Lee said that the defence and foreign affairs ministries already have separate computers for Internet access and for handling sensitive communications.
There was a huge backlash on Wednesday when The Straits Times newspaper reported that some 100,000 government computers would be affected by the Internet blockage, aimed at keeping data secure and preventing the spread of malware.
It quoted a cyber security official as saying that there were 16 attacks on government systems from unnamed sources in the last year, but the malware was detected and destroyed.
Malware is software specifically designed to disrupt or damage a computer system.
Civil servants would still be able to access the Internet on their personal devices such as tablets and mobile phones.
Public-school teachers and lecturers would not be affected by the move, officials said.
Singapore is one of the world’s most Internet-savvy societies, offering broadband speeds envied by many.
A wide range of government services are available online, including registering for marriage, filing complaints to the police and video consultations with doctors.
Singapore announced in 2014 it was stepping up IT security measures following attacks on a section of the prime minister’s website, as well the website of the presidential residence.