The European Union will organize a conference to locate children kidnapped in Ukraine by Russia and bring them back to their country, European Commission President Ursula von der Leyen announced Thursday after a summit in Brussels. “It’s a horrific reminder of the darkest times in our history, the child deportations that happen there. This is a war crime,” the German official said after a summit in Brussels.

“We know that 16,200 children were deported, only 300 have since returned,” she continued at a press conference. She added that “these criminal actions fully justify the arrest warrants issued by the International Criminal Court” on March 17 against Russian President Vladimir Putin and Russian Presidential Commissioner for Children’s Rights Maria Lvova-Belova for “unlawful deportation of Ukrainian children during the Russian invasion.

The aim is “to assist UN bodies and relevant international organizations to obtain more comprehensive information” on deported children, she said. “This also includes children who have been adopted or transferred to Russian foster families,” she said. She thanked UN Secretary General Antonio Guterres, who was present at the summit on Thursday in Brussels, for the support of UN agencies on this issue.