More than 13,000 Ukrainian children have been taken to Russia from Ukraine since the February invasion, an advisor to President Volodymyr Zelenskyy said Friday, adding that the actual figure was likely much higher.At a press briefing in Kyiv, Darya Gerasimchuk, an advisor charged with protecting children's rights, said the authorities in Moscow had "deported or relocated" the kids from areas occupied by Russian forces.Under the Geneva Conventions, it is a crime for a warring party to transfer another country's children to its own territory unless there are "imperative reasons" to do so, in which case "all necessary steps must be taken to facilitate the return of the children to their families and their country."According to Ukraine's National Information Bureau, which was created in March to document casualties and alleged war crimes, no fewer than 13,112 children have been "deported" since Russia invaded the country.In May, Russia changed its laws to allow Ukrainian children to be granted Russian citizenship, paving the way for them to be given to Russian families."