The Ukrainian First Lady, Olena Zelenska, is visiting the UK to highlight the plight of the Ukrainian people.
During her visit on Tuesday, she addressed the House of Commons, thanking Britain for its support in the war against Russia.
"I urge you, members of parliament, to help us unite the global community as much as possible. Unite the world in support of a special tribunal for Russian crimes against Ukraine," said the First Lady.
"Today, I am asking you to become a world leader of justice. Nothing more, nothing less," she concluded, receiving a standing ovation.
The speech comes as Ukraine enters its ninth month of conflict with Moscow's forces.
Preventing sexual violence in conflict
The First Lady also attended the Preventing Sexual Violence in Conflict Initiative conference in London.
She demanded a "global response" to the use of sexual violence as a weapon of war.
Olena Zelenska claimed Ukrainian prosecutors are currently investigating more than 100 possible crimes by Russian soldiers.
The Ukrainian government has launched a support programme to help victims of the war, which Zelenska said she hoped could be a "first step towards an investigation and prosecution".
Ukraine is looking to set up similar initiatives outside the country, such as in Germany and the Czech Republic, she added.