Children in Russian-occupied areas of Ukraine have been variously removed or forced to sit school lessons in Russian.
ADVERTISEMENTQatar said on Monday it had reunited with their families in Ukraine four Ukrainian children who were on Russian territory after being taken by the Moscow authorities following the invasion in February 2022.
"Qatar announces the successful completion of an operation to reunite a number of Ukrainian children with their families," the foreign ministry in Doha said in a statement.
It said it hoped the operation would mark "the beginning" of a process to repatriate more children to Ukraine.
The ministry explained that last week it had brought together the children and their families at the Qatari embassy in Moscow, before "transporting them to their final destination" in Ukraine.
A Qatari diplomatic source close to the case said that four children were able to reach Ukraine on Monday, describing the operation as a "breakthrough" and a "gesture of goodwill" on the part of Russia.
For its part, the Qatari Foreign Ministry said that the "success of the operation testifies to the credit Qatar enjoys with the various parties (in conflict) and its ongoing quest for peace and stability in the region and the world".
Kyiv has accused Moscow of deporting "tens of thousands" of Ukrainian children who were "kidnapped" in the occupied territories of Ukraine.
The International Criminal Court has issued an arrest warrant for Russian President Vladimir Putin for the "illegal deportation" of thousands of Ukrainian children since February 2022.
Moscow rejects these allegations.
According to the wife of the Ukrainian president, Olena Zelenska, more than 19,000 Ukrainian children have been transferred or taken by force to Russia or to occupied regions.
Only 386 have been returned to Ukraine, she told a press conference on the sidelines of the UN General Assembly in New York on 20 September.
Qatar plays the role of mediator in many international affairs. It recently facilitated an agreement on a prisoner exchange between the United States and Iran, which included Washington lifting its freeze on six billion dollars of Iranian assets.