Russia was accused by Ukraine of forcibly transferring Ukrainian civilians out of the occupied territory and moving them into Russia, in allegations made by Ukrainian Foreign Ministry spokesperson Oleg Nikolenko on Monday and the Mariupol city council on Sunday.
Nikolenko alleged that Russian forces had relocated 2,389 children from the separatist Donbas into Russia on Saturday.
"Abducting civilians is strictly prohibited by international humanitarian law," said Nikolenko. "The Russian army deprives our children of parental care and endangers their lives in Russia. These heinous crimes must be stopped."
The Mariupol city council alleged on Sunday that Russian forces had transferred Mariupol area residents to Russia or to the separatist Donbas region.
The leadership of the besieged port city claimed that the expelled residents had their Ukrainian passports confiscated, and had been issued new identification papers.
This report came after a Mariupol school sheltering 400 Ukrainian civilians was reportedly hit by a Russian airstrike on Saturday.
"Every war criminal will be held accountable for his crimes against humanity, against the people of Mariupol," the city council said in a statement.