Russia is considering a freeze on child adoptions by US families after a boy was put on a one-way flight back Moscow.

Artyom Savelyev, eight, arrived in Moscow unaccompanied on a United Airlines flight from Washington on Thursday.

His adopted grandmother, Nancy Hansen, said she put the child on a plane to Russia with a note from her daughter Torry.

She said the family paid a man $200 US dollars to pick the boy up at the airport and take him to the Russian Education and Science Ministry. She added that boy had been violent toward his adoptive mother in the US.

The children's office said the boy, whose adopted name is Justin Hansen, was carrying a letter from his adoptive mother, Torry Hansen of Shelbyville, Tennessee, saying she was returning him due to severe psychological problems.

Russian Foreign Minister Sergey Lavrov said: "We have taken the decision, and Russian Foreign Ministry will stand for this firmly, to freeze, to suggest a freeze on any adoptions to American families until Russia and the USA sign an international agreement about the conditions of adoption and responsibilities of the families which take our children."

The US ambassador to Russia, John Beyrle, said he was "deeply shocked by the news" and "very angry that any family would act so callously toward a child that they had legally adopted."