A Russian official involved in what international prosecutors call the illegal deportation of Ukrainian children, claimed by the Kremlin to be an effort to protect them from "Nazism," was associated online as a teenager with white supremacist and neo-Nazi movements, Reuters has found.

The material posted online by Alexei Petrov between 2011 and 2014 remained on his social media account until late July this year when, following questions posed by Reuters, he deleted some videos, unsubscribed from two far-right online groups, and made one of his accounts private.

Petrov is a 27-year-old advisor in the office of Maria Lvova-Belova, Russia's presidential commissioner for children's rights. In March, the International Criminal Court issued arrest warrants for Lvova-Belova, along with Russian President Vladimir Putin, on charges of committing a war crime by forcibly deporting hundreds of children from Ukraine and taking them to Russia.