More than 200,000 children have been abducted by Russia since the start of its invasion of Ukraine, Chairman Emeritus of the House Foreign Affairs Committee Michael McCaul, R-Texas, said, citing U.S. estimates.

"If a foreign adversary took 260,000 of our kids, and they were in indoctrination camps, I mean, how would we feel about that?" McCaul asked Fox News Digital.

The Texas Republican was recently term-limited in his time as chairman of the foreign affairs panel, but he is continuing to work on the world stage, in part by raising awareness about Russia’s atrocities in Ukraine. Among the most egregious is the relocation of thousands of Ukrainian children into Russia, the vast majority of whom have not been returned.

Some parents would be coerced into giving up their children because Russian forces were threatening to bomb their city, McCaul said, while other times "they just invade and capture the children."

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The International Criminal Court issued arrest warrants in February 2023 for Russian President Vladimir Putin and Russia’s commissioner for children’s rights, Maria Lvova-Belova, "for the war crime of unlawful deportation of [children] and that of unlawful transfer of [children] from occupied areas of Ukraine."

Lvova-Belova was sanctioned last year by the U.S. over her part in the scheme, which has been widely condemned by western governments.

However, the Kremlin has denied war crime allegations and maintained it is doing humanitarian work facilitating homes for Ukrainian children, NPR reported.

Existing accounts from returned children and elsewhere paint a picture of forced indoctrination within Russia’s borders, however. Some of those children are given military training, according to the Yale Humanitarian Research Lab, likely in preparation to fight on Russia’s front lines.

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Estimates on how many children have been taken to Russia vary between 20,000 to upwards of 250,000.

Part of McCaul’s work raising awareness about Russia’s treatment of Ukrainian children will include a screening of a documentary titled, "Children in the Fire: Ukraine’s War Through the Children’s Eyes" by filmmaker Evgeny Afineevsky, at the Munich Security Conference next month.

He has also worked with the nonprofit Save Ukraine, which is working to return children.

"In the documentary, the child's brought into this prison where it looks like adults are being— basically they're using electrodes to shock them, you know, under their fingernails and their genitals, and it's just very, very barbaric," McCaul said.

He also held a hearing last year on the issue while leading the foreign affairs committee.

McCaul said Russia’s abduction of children is among the most vile of its alleged violations of the Geneva Conventions. He compared it to infamous Nazi physician Josef Mengele’s experiments on Jewish children and adults.

"It's just evil. I mean, any civilization that would capture— I mean, it's one thing if you're on the battlefield killing the enemy, from their point of view," McCaul said. "But to capture the children to re-indoctrinate them is sort of reminiscent of, you know, Mengele’s experiments on kids…And I don't think we've seen anything like this in recent society."

The House passed a resolution last year condemning Russia’s abduction of Ukrainian children in a bipartisan 390 to 9 vote.

"It's just horrific. I can't imagine, as a father, my children being, you know, taken away by the Russian Federation and then not knowing where they are or what's happening to them," McCaul said. "But this is all part of Putin's game, is to try to indoctrinate the children in Ukraine to go against their own country and belief system."