According to a US study, Russia has sent at least 6,000 Ukrainian children to re-education camps, possibly committing war crimes. Experts identify 43 such camps in Russia and Russia’s annexed Crimea peninsula in a Yale Humanitarian Research Lab report released on Tuesday.

Children as young as four months old have been taken to Russian camps since Russia’s war of aggression against Ukraine began almost a year ago, according to the study funded by the US State Department. The aim is, among other things, “pro-Russian patriotic” and military-style education. In some cases, children received firearms training. However, there is no indication that the children were sent to war.

Yale researcher Nathaniel Raymond said Russia’s actions represent a “clear violation” of the Fourth Geneva Convention for the Protection of Civilians in War. In some cases, it could amount to “a war crime and a crime against humanity.” Raymond likened the Russian actions to kidnappings. The authors of the study call for independent observers to have access to the camps and for an end to Russian adoptions of Ukrainian children.

The study is based, among other things, on the evaluation of satellite images. Accordingly, the actual number of Ukrainian children brought to the camp is likely to be “significantly higher” than the at least 6,000 identified.

Russia has denied the allegations as “absurd statements”. The children and their relatives were being taken to safety from being shelled by Ukrainian forces, the Russian embassy in the United States said on Wednesday. “We do everything we can to keep the underage citizens with their families — and in the event of the absence or death of parents and loved ones, to give care to the orphans.”

The Russian embassy claimed that the “Kiev regime” was responsible for the deaths and injuries of children. Last year, 153 children were killed in Donbass, which was occupied by Russian troops, as a result of Kiev’s “actions” and weapons supplied by the West. 279 children were injured.

The Ukrainian armed forces would strike civilian infrastructure with US Himar-type multiple rocket launchers, which would also hit schools, kindergartens and hospitals, the embassy claimed. Ukraine also repeatedly accuses Russian troops of shelling such civilian facilities.