Hundreds of children have been taken from Ukrainian orphanages and boarding schools to Russia, the chief prosecutor of the International Criminal Court, Karim Khan, said today.

Khan’s statement came after the ICC issued arrest warrants against Russian President Vladimir Putin and Maria Alekseevna Lvova-Belova, the Russian presidential commissioner for children’s rights.

The ICC accuses Putin of being “responsible for the war crime of the illegal deportation of a population (of children) and the illegal transfer of a population of (children) from the occupied territories of Ukraine to the Russian Federation.”

“Many of these children, we claim, have since been given up for adoption in the Russian Federation,” he said.

Khan stressed that a change in Russian law made it easier for children to be adopted by Russian families, while at the time of the deportations, Ukrainian children were protected persons under the Fourth Geneva Convention.

In his statement, Khan called today’s arrest warrants “a first concrete step” while other investigations into Ukraine are ongoing.