Ukraine's ambassador and diplomats from a wide number of countries staged a walkout on Tuesday as Russia's foreign minister addressed the Conference on Disarmament in Geneva.
The diplomats stood up and left the room when Sergei Lavrov's pre-recorded video message began to play, in protest at Moscow's invasion of Ukraine, according to an AFP journalist in the room.
Ukrainian Ambassador Yevheniia Filipenko was among the numerous diplomats who filed out as the video began playing, leaving the room almost empty.
Outside they gathered in front of a Ukrainian flag and broke into strong applause that could be heard in the chamber where Lavrov's speech continued, with only a handful of ambassadors from countries including Yemen, Syria, Venezuela and Tunisia remaining to hear him.
"It is important to show a gesture of solidarity with our Ukrainian friends," said French ambassador Yann Hwang.
Russia's top diplomat had been scheduled to go to Geneva to address both the UN-linked disarmament body and the UN Human Rights Council in person Tuesday, but cancelled at the last minute, with Moscow blaming "anti-Russian sanctions" imposed by EU countries.
Russia has become an international pariah since launching a full-scale invasion six days ago.
"Russian indiscriminate attacks on civilian and critical infrastructure are war crimes and violations of the Rome Statute," Ukraine's foreign minister told the disarmament meeting before Lavrov spoke.
"Russian aggression is a global threat," he warned, insisting that "the response too must be global."
In his speech, Lavrov blamed Kyiv for the crisis, warning it was trying to assemble nuclear weapons.
"I can assure you, Russia as a responsible member of the international community... is taking all necessary measures to prevent the emergence of nuclear weapons and related technologies in Ukraine," he said.