Ukraine said on Friday Russia had forcibly deported more than 210,000 children since its invasion on Feb. 24 and accused Moscow of wanting to make them Russian citizens.
Human rights ombudswoman Lyudmyla Denisova said the children were among 1.2 million Ukrainians who Kyiv says have been deported against their will.
"When our children are taken out, they destroy the national identity; deprive our country of the future.
"They teach our children there, in Russian, the history that (Russian President Vladimir) Putin has told everyone," Denisova
Moscow has denied intentionally targeting civilians since launching what it calls a special military operation in Ukraine and says it is offering humanitarian aid to those who want to leave Russia.
Russia has referred to "refugees" coming to Russia to escape fighting, particularly from the southern Ukrainian city of Mariupol, which is in Russian hands after weeks of siege and bombardment.
The 1949 Geneva Conventions, which define international legal standards for humanitarian treatment in conflict, prohibit mass forcible transfers of civilians during a conflict to the territory of the occupying power, classifying it as a war crime.