The European Parliament website was briefly affected by a hacking attack, officials said on Wednesday.
Parliament President Roberta Metsola said it was a "sophisticated attack" and that a pro-Kremlin group had claimed responsibility.
She noted that the attack followed the EU lawmakers' vote to name Russia a "state sponsor" of terrorism over its war in Ukraine.
"My response is: Slava Ukraini (Glory to Ukraine)," Metsola said.
The website was up again around two hours after European Parliament officials first reported the attack.
Parliament spokesman Jaime Duch said the website was down due to a Distributed Denial of Service (DDoS) attack.
DDoS attacks involve a website being flooded with simultaneous and coordinated webpage requests from multiple computers. This makes it difficult for the website to handle all of the requests, and therefore becomes extremely slow or completely inaccessible to legitimate users.
"Today's attack on the European Parliament's systems is a warning shot. It is an attack on the democratic heart of Europe," said German Member of European Parliament (MEP) Rasmus Andresen.
EU lawmakers declare Russia 'state sponsor' of terror
Just hours before the attack, MEPs voted overwhelmingly to declare Russia a "state sponsor" of terrorism, arguing that Moscow's strikes on civilian targets amounted to "war crimes."
"The deliberate attacks and atrocities committed by Russian forces and their proxies against civilians in Ukraine, the destruction of civilian infrastructure and other serious violations of international and humanitarian law amount to acts of terror and constitute war crimes," a press release from the European Parliament stated.
The designation is largely symbolic, and Russia will likely not face any hard and fast legal sanctions.
Sergey Lagodinsky, a member of the European Parliament for the Green Party, told DW that the terminology "does have consequences," adding it was also an "important sign" to Kyiv.
"This gives Russia a very clear description of what they are doing,"Lagodinsky said.
Ukrainian President Volodymyr Zelenskyy, who had pleaded for the designation, welcomed the move by parliament. He called for Moscow to be "isolated at all levels and held accountable."
fb/dj (AFP, AP, Reuters)