Konstantin Dolgov, of the Russian foreign ministry, said U.S. authorities should "conduct an appropriate investigation into the facts of gross violations of children's rights that been uncovered," RIA Novosti reported Saturday.
Dolgov's statement on Friday alluded to a report by an American media organization that some U.S. families were using social media to carry out informal transfers of their foreign-born adopted children.
The practice, known as "re-homing," circumvents monitoring by child welfare agencies.
"We believe that the matter is not about individual cases but a serious systemic problem showing that children's rights in the U.S. are not protected properly," Dolgov said.
U.S. authorities also should clarify the fate of 26 Russian children "who have fallen victim to the U.S. Internet-exchange of adoptees," Dolgov added.
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