As Russian forces laid siege to the Ukrainian city of Mariupol last spring, children fled bombed-out group homes and boarding schools. Separated from their families, they followed neighbors or strangers heading west, seeking the relative safety of central Ukraine.

Instead, at checkpoints around the city, pro-Russia forces intercepted them, according to interviews with the children, witnesses and family members. Authorities put them on buses headed deeper into Russian-held territory.

"I didn’t want to go,” said Anya, 14, who escaped a home for tuberculosis patients in Mariupol and is now with a foster family near Moscow. "But nobody asked me.”