Pro-Russian hackers have attacked the websites of several Italian institutions, including the senate, ANSA news agency reported on Wednesday.
The hacker group "Killnet" claimed the attack, ANSA said, which also involved the National Health Institute (ISS) and the Automobile Club d'Italia, a national drivers' association.
The websites of the senate and the ISS were back online at 8.00 p.m. (1800 GMT). It was impossible to access them one hour earlier.
The defence ministry, whose website was not available, said in a statement this was "due to long-planned maintenance activities ongoing on the website".
A source at the Italian cyber security agency told Reuters they were working with the affected administrations to restore the websites, suggesting "the first appropriate technical countermeasures".
Police said an investigation was ongoing, but made no further comment.
After Russia's invasion of Ukraine, many western governments have raised the level of alert over possible cyber attacks on IT systems and infrastructure.
Late in March, Italian railway company Ferrovie dello Stato Italiane (FS) temporarily halted some ticket sale services fearing it had been targeted by a cyber attack.
In April, the ecology transition ministry said it had to shut down all its IT systems due to external threats.
