A pro-Russia hacker group known as "Killnet" claimed a cyberattack on websites belonging to several Italian institutions on Wednesday, Italy's ANSA news agency and several other domestic outlets including newspaper Corriere della Sera reported.

As of Wednesday evening, websites belonging to Italy's defense ministry, Senate and National Health Institute were not functioning.

The Defense Ministry's website said it was "under maintenance" and the Senate's was also inaccessible.

Police said an investigation was ongoing but provided no further details. Italy's Defense Ministry and cybersecurity agency have not commented.

Governments on alert for hackers

Since Russia's invasion of Ukraine, Western governments have been on the alert for cyberattacks targeting public institutions.

On Monday, German officials confirmed a series of attempted cyberattacks the previous week on government agencies.

Interior Ministry spokesman Maximilian Kall said that no data was leaked, and that the attacks were successfully repelled without any permanent damage caused.

The attacks were directed against the Defense Ministry, the Bundestag, federal police and several state police authorities, with news magazine Der Spiegel first breaking the story. Killnet hackers claimed responsibility.

Last month, Romanian intelligence services said Killnet targeted Romanian government websites in response to Bucharest's support for Ukraine.

Officials said the hacker group has also targeted official websites of the United States, Poland, the Czech Republic, Estonia and NATO.

Killnet is known to specialize in so-called Distributed Denial of Service (DDoS) attacks, in which hackers try to paralyze servers with a flood of requests.

This then makes the website extremely slow or completely inaccessible to legitimate users.

wmr/msh (Reuters, AFP, dpa)