Russia has released a "catalogue" of kidnapped Ukrainian children up for adoption, sorted by hair and eye colour.
The listing, launched by Russian authorities running Ukraine's eastern Luhansk region, holds information on 294 children.
CEO of the Save Ukraine organisation, Mykola Kuleba - who brought the scandal to light - said: "Since 2014, children from the occupied territories - Luhansk, Donetsk and Crimea - have been systematically transported to the order of Russian families under Moscow and to other regions of Russia.
"It would appear that demand for children has decreased, so the occupiers are looking for new ways to 'improve' this terrible system."
He added: "Most children in this 'catalogue' were born before the occupation of Luhansk region and had Ukrainian citizenship.
"The parents of some of them were killed by the occupation authorities, the others just made Russian documents to legalise kidnapping."
Photos of the children are presented alongside their age, gender, and personality traits, with some being described as "obedient" and "calm".
SAVE UKRAINE
|Russia has rolled out a disturbing database said to contain kidnapped Ukrainian children up for adoption, sorted by hair and eye colour
The database allows prospective parents to filter by age, eye and hair colour, as well as their preferred form of guardianship, such as adoption or foster care.
Kuleba added: "The way they describe our Ukrainian children is not different from the slave catalogue.
"This is real child trafficking in the 21st century that the world needs to stop immediately."
Official figures have identified nearly 20,000 Ukrainian children who have been kidnapped by Russia, but the real number is expected to be much higher.
REUTERS
|Current official numbers state nearly 20,000 Ukrainian children have been kidnapped by Russia, but the real number is thought to be much higher
GETTY
|Russia's Children's Commissioner, Maria Lvova-Belova, has been hit with an arrest warrant by the International Criminal Court
Daria Herasymchuk, the Advisor and Commissioner of the President of Ukraine for Children's Rights and Rehabilitation, has put the number between 200,000 to 300,000.
Currently, fewer than 1,500 have been returned to their homes.
Both Putin and Russia's Children's Commissioner, Maria Lvova-Belova, have been hit with arrest warrants by the International Criminal Court (ICC) over child abduction.
They were accused of transferring children to Russia having unlawfully deported them from occupied areas of Ukraine.
In March 2023, the ICC said Putin "bears individual criminal responsibility" as Russia's President, while alleging both those accused had been committing the crimes since at least February 2022.
But Russia's Foreign Ministry dismissed the accusations at the time, blasting: "Decisions of the International Criminal Court have no meaning for our country, including from a legal standpoint."
Russia left the ICC in 2016 after its illegal annexation of Crimea.