Technicians were working to "mitigate the consequences" of the attack, it wrote in a statement, adding that initial checks showed no evidence of data theft.
It was too early to predict when activities would be back to normal, it said.
The attack began in the early morning.
The ministry said it was in close contact with the National Cybersecurity Agency to reduce inconvenience for citizens and businesses.
(Reporting by Alessia Pé, editing Gianluca Semeraro and Nick Macfie)
