At a parliamentary meeting of the European security body in Vienna, many attendees left during a Russian speech.
It happens as the UN is about to vote on a resolution denouncing Russia's invasion of Ukraine.
One day ahead of the anniversary of the invasion of Ukraine, on Thursday, the Organization for Security and Co-operation in Europe (OSCE) was established.
However, the choice to grant visas to the Russian delegation has stoked resentment.
Due to Austria's decision to invite officials from Moscow despite some of them being subject to EU sanctions, Ukraine and Lithuania boycotted the meeting entirely.
The Austrian government claims that because the OSCE's headquarters are there, it was required to comply under international law.
Russian participation was referred to as the "elephant in the room" by Latvian MP Rihards Kols, who also called it a "disgrace" that they were permitted to participate.
Following that, a sizable contingent of attendees staged a walkout during the Russian address.
Vladimir Dzhabarov, a Russian delegate, mocked other delegates for leaving the meeting and repeated untrue claims that Russia's invasion of Ukraine was an effort to oust nationalists and Nazis who, according to Moscow, were in charge of the Kyiv government.
To foster better ties between the Western and Eastern Blocs, the OSCE was established in 1975. Members of NATO and Russian allies are currently included in its membership.
The protest took place before the UN General Assembly voted on a resolution denouncing the invasion of Ukraine and urging swift peace. In New York, the vote is scheduled for Thursday night.
Despite not having legal force, the measure has political influence.
The vote, according to British ambassador to the UN Barbara Woodward, "would keep pressure on Russia to end the war.".
However, some nations, such as Belarus, China, and Iran, claim that the text inflames tension and promotes a Cold War mindset.
"It is high time to step back from the brink," UN Secretary-General António Guterres said to the UN General Assembly on Wednesday. ".
War is not the answer. The issue is war. Ukraine's citizens are going through a lot of pain. "Peace is necessary for Ukrainians, Russians, and people everywhere," he said.
The largest European invasion since the end of World War Two began on February 24, 2022, when President Vladimir Putin sent up to 200,000 soldiers into Ukraine.
According to a UN estimate, the devastating war that followed has resulted in at least 7,199 civilian deaths and thousands of other injuries, though the actual toll is probably much higher.
Volodymyr Zelensky, the president of Ukraine, paid tribute to all those who have perished in the conflict.
Mr. Zelensky vowed to hold Moscow accountable for "all the terror, all the killings, all the torture" in a Telegram post.