Germany has summoned a top Russian envoy over a series of cyberattacks targeting members of the governing Social Democrats and its defense, technology and logistics sectors.

According to The Guardian, Germany blames the 2023 attacks on a hacker group, Fancy Bear, linked to Russian military intelligence. Using a then-unknown vulnerability in the Microsoft Outlook email service, the group knocked several websites offline, and compromised the servers of affected companies, apparently as a reprisal for Berlin’s decision to send tanks to Ukraine.

Germany’s interior ministry said a series of cyber-attacks attributable to the Russian military intelligence service GRU had also targeted the country’s logistics, defense, aerospace and IT sectors, exploiting the vulnerability in Microsoft Outlook in order to compromise email accounts.

“Today we can say unambiguously [that] we can attribute this cyber-attack to a group called APT28, which is steered by the military intelligence service of Russia,” the German foreign minister, Annalena Baerbock, told a news conference during a visit to Australia. “In other words, it was a state-sponsored Russian cyber-attack on Germany, and this is absolutely intolerable and unacceptable and will have consequences.”

The Czech Republic said its institutions had also been targeted.

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APT28, also known as Fancy Bear or Pawn Storm, has been accused of dozens of cyber-attacks in countries around the world. The U.K.’s National Cyber Security Centre has described the unit as “a highly skilled threat actor” that has “used tools including X-Tunnel, X-Agent and CompuTrace to penetrate target networks.”