The hacker group Noname057(16) claimed the cyber attack on Telegram, saying Italy's "Russophobes get a well deserved cyber response".
In such attacks, hackers attempt to flood a network with unusually high volumes of data traffic in order to paralyse it.
The spokesperson said the agency provided quick assistance to the institutions and firms targeted and that the attack's impact was "mitigated" in less than two hours.
The cyber attack has not caused any disruptions to flights at Milan's Linate and Malpensa airports, a spokesperson for SEA, the company which manages them, said.
While the websites were inaccessible, the airports' mobile apps continued to function, the SEA spokesperson added.
MNA/