The International Criminal Court on Friday announced it had issued an arrest warrant against Russian President Vladimir Putin for the "unlawful deportation" of Ukrainian children.
The Hague-based ICC said it had also issued a warrant against Maria Lvova-Belova, Russia's presidential commissioner for children's rights, on similar charges.
Russia is not a member of the ICC. It was unclear how the ICC planned to enforce the warrant.
"Today, pre-Trial Chamber II of the International Criminal Court issued warrants of arrest for two individuals in the context of the situation in Ukraine: Mr Vladimir Vladimirovich Putin and Ms Maria Alekseyevna Lvova-Belova," the ICC said in a statement.
Vladimir Putin "is allegedly responsible for the war crime of unlawful deportation of population (children) and that of unlawful transfer of population (children) from occupied areas of Ukraine to the Russian Federation."
The ICC said the crimes dated from February 24, 2022, when Russia invaded Ukraine.
"There are reasonable grounds to believe that Mr Putin bears individual criminal responsibility for the aforementioned crimes," it said.
President Putin was allegedly responsible both directly by committing the acts and for "failure to exercise control properly over civilian and military subordinates who committed the acts, or allowed for their commission."
The arrest warrants are being kept secret to protect victims and witnesses, it said.
The ICC is a court of last resort for crimes that countries cannot or will not prosecute war crimes and crimes against humanity.
ICC prosecutor Karim Khan launched an investigation into alleged war crimes and crimes against humanity in Ukraine just days after Russia's invasion.