UNITED NATIONS, UNITED STATES (AFP) - Ukrainian children should not be adopted in Russia, where several thousand young people are believed to have been moved since Moscow's February invasion, a UN official said on Tuesday (June 14).

"We're reiterating, including to the Russian Federation, that adoption should never occur during or immediately after emergencies," Asfhan Khan, the UN Children's Fund (Unicef) regional director for Europe and Central Asia, told reporters.

Such children cannot be assumed to be orphans, and "any decision to move any child must be grounded in their best interests and any movement must be voluntary. Parents need to provide informed consent," said the official, who had just returned from a visit to Ukraine.

"Regarding children that have been sent to Russia, we're working closely to see with ombudspersons and networks how best we can document those cases," Khan said, adding that there is currently no access to those children.

The United Nations had already expressed concern in early March about the risk of forced adoption of Ukrainian children, especially the some 91,000 who were living in institutions or boarding schools at the beginning of the war, many of them located in the country's east.