Ukraine is seeking international help to repatriate thousands of children who Kiev says have been kidnapped to Russia.

There are at least 11,000 children whose names are known, said President Volodymyr Zelenskyj in his evening video address on Monday. "But those are just the ones we know about. In fact, more have been abducted."

The head of the presidential office in Kyiv, Andriy Yermak, discussed the problem in a large online conference on Monday. UN Secretary General Antonio Guterres and the ambassadors of the Group of Twenty large industrialized and emerging countries (G20) also took part. The annual G20 summit is currently taking place in Indonesia.

Yermak: Do everything to get children back

"Our goal is to stop the violent kidnapping or deportation of children from Ukraine to the Russian Federation," said Yermak, according to official statements. Everything must be done to bring these children back and reunite them with their families.

The Russian military and Russian authorities do confirm that children are being brought to Russia from Ukraine. They would be taken to safety from the combat zones or come to Russia for treatment or recovery. There are also reports of Ukrainian children being put up for adoption in Russia. The Ukrainian child rights officer Dariya Gerassymtschuk spoke of 10,764 abducted children.

Selenskyj thanked Guterres for his willingness to take on the issue of the children. "It takes the power of the whole world to bring back all the deportees," he said.