As part of a summit with Ukrainian President Volodymyr Zelenskyy in Kyiv that continued Friday, leaders with the European Union (EU) announced Thursday it will set up the “International Center for the Crime of Aggression in Ukraine.” The center will serve as the latest effort to punish Russian officials for alleged war crimes committed during the invasion.

“This center will coordinate the collection of evidence. It will be embedded in the joint investigation team, which is supported by our agency Eurojust,” European Commission President Ursula von der Leyen said Thursday. “Russia must be held accountable in courts for its odious crimes.”

The crime of aggression is often called the “mother of all crimes” because it is a transgression from which other war crimes flow. Thursday’s announcement came as the EU and international community as a whole consider creating a special international tribunal for the specific purpose of prosecuting senior Russian officials for the crime of aggression.

President Zelenskyy and EU leaders were also expected to discuss further sanctions against Russia and more aid for Ukraine. The summit came as the United States was expected to announce Friday it will send longer-range bombs to Ukraine as part of a new $2.17 billion aid package. EU leaders also spoke about Ukraine’s prospect of joining the bloc.

“You prepared your application for European Union membership brilliantly,” von der Leyen said. “You became a candidate country while fighting an invasion. You continue to make impressive progress to meet the seven steps of the Commission’s opinion.”

The EU has demanded more anti-corruption measures from Ukraine. Zelenskyy has announced dismissals and investigations of some officials over the past two weeks, saying the country’s defense ministry needs to be cleaned up.

“The only way to guarantee legitimacy is to change leaders along with institutional changes implementation,” Zelenskyy said Wednesday. “Change as much as necessary to ensure that people do not abuse power.”

The Associated Press, Reuters and Voice of America contributed to this report.