Yale researchers say more than 2,400 children have been deported from Russian-occupied parts of Ukraine.

The report (PDF), released on Thursday, said at least 2,442 children aged between six and 17 years old had been taken to 13 facilities across Belarus since Russia began its full-scale invasion in February 2022 until the end of October this year.

“Russia and Belarus are targeting children for removal from Ukraine, coordinating their transport from occupied Ukraine through Russia to Belarus, and subjecting children to re-education, sometimes including military training, sometimes including military training,” the Yale HRL researchers said.

They said Belarus’s authoritarian leader, Alexander Lukashenko, a close ally of Russian President Vladimir Putin, had “jointly directed and co-funded” the deportations with Putin under the Union State initiative that was first agreed back in 1996.

“Belarus’s direct involvement in Russia’s forced deportation of children represents a collaboration between Belarus’s authoritarian leader [Alexander] Lukashenka and Russia’s President Vladimir Putin, with various pro-Russia and pro-regime organisations facilitating the deportation,” they said.

Putin is already the subject of an International Criminal Court arrest warrant over Moscow’s alleged forcible transfer of Ukrainian children from occupied territories, along with the country’s Children’s Commissioner Maria Lvova-Belova.

Taking children under the age of 18 across a border without the consent of a parent or guardian is illegal under international humanitarian law.

Kyiv, which estimates some 19,000 children have been abducted, has already said it is investigating Belarus’s alleged involvement in the policy.

In September, Belarus’s state media published photos of dozens of Ukrainian children arriving in the country from the Donetsk, Luhansk and Zaporizhia regions for a “three-week holiday”. The children were shown getting off a train carrying backpacks and suitcases, mostly looking solemn.

Alexei Talai, the head of the charity leading the programme, said Lukashenko had described it as an “important humanitarian project” that needed to continue. Talai was also mentioned as a facilitator in Thursday’s report.

The Yale HRL is part of The Conflict Observatory, which receives funding from the United States.

“These revelations of Belarusian involvement are part of a broader campaign directed by Russia,” the US State Department said in a statement.

“Members of Russia’s military and government have deported hundreds of thousands of Ukraine’s civilians to Russia, including children who have been forcibly separated from their families. The United States will continue to pursue accountability for actors involved in abuses connected with Russia’s war against Ukraine.”

Moscow has denied allegations that it is involved in forcible transfers or separating children from their families.

The Yale HRL report said the children had been taken from at least 17 cities in Ukraine’s eastern Donetsk, Luhansk, Kherson and Zaporizhia regions, parts of which are occupied by Russia.

They were put on trains to Rostov-on-Don in Russia before being transported to Belarus.

It said more than 2,050 of the children had been taken to the “Dubrava children’s camp” in Minsk, the Belarusian capital.

The researchers said it was not clear how many of the children it had documented remained in Belarus.