Children were transported from the Russian-controlled city of Kherson on a bus heading to Crimea last year.
Ukrainian Deputy Prime Minister Iryna Vereshchuk has urged russians not to adopt children who she said were "stolen" in Ukraine during the war and deported to russia.
The war that russia has been waging on its neighbour for 13 months now has seen millions of people displaced, including families and children.
The real number of children who have been forcefully deported to russia is impossible to establish.
The International Criminal Court (ICC) issued an arrest warrant earlier in March against russian President vladimir putin and Maria Lvova-Belova, russia's commissioner for children's rights, accusing them of the war crime of illegally deporting hundreds of children from Ukraine.
Ms Vereshchuk said on the Telegram messaging app that orphans have been "stolen in Ukraine" and allegedly given up for adoption in russia.
Iryna Vereshchuk urges russian citizens not to adopt orphans she says were illegally taken from Ukraine.
"I strongly recommend that russian citizens do not adopt Ukrainian orphans who were illegally taken out of the temporarily occupied territories of Ukraine," Ms Vereshchuk said.
"Once again I remind all russian so-called 'adoptive parents' and 'guardians': sooner or later you will have to answer."
Both vladimir putin and Maria Lvova-Belova have been issued an arrest warrant by the International Criminal Court.
Both vladimir putin and Maria Lvova-Belova have been issued an arrest warrant by the International Criminal Court.
Russia has not concealed a program under which it has brought thousands of Ukrainian children to russia, but presents it as a humanitarian campaign to protect orphans and children abandoned in the conflict zone.
Most of the movement of people and children occurred in the first few months of the war and before Ukraine started its major counter offensive to regain occupied territories in the east and south in late August.
Russia's defence ministry said in mid-August that 3.5 million people had been brought to russia by then, including more than half a million children.
The United States said in July that russia "forcibly deported" 260,000 children, from their homes to russia.
Russian TASS agency cited Vitaly Ganchev, moscow-installed official of russia-occupied parts of the Kharkiv region, as saying on Tuesday (local time) that a group of children from the region was sent to russia last year with the consent of their parents or guardians.
"The children were placed in excellent conditions, they are provided with everything necessary. And we will continue to take care of them until their parents come for their return," Mr Ganchev added.
