Moscow: Moscow has sought a thorough investigation by the United States authorities in a case related to rape by a US national of his foster Russian daughter.

Russian Foreign Ministry spokesman Alexander Lukashevich stated the demand on Thursday.

“We demand that the US authorities hold an all-embracing and thorough investigation into the assault of Ksenia and hand down a just verdict to the guilty party,” Lukashevich said.

The accused Gismore's lawyers claim that Ksenia was 16 years old, when their client had sexual intercourse with her. In line with the laws of Georgia, 16 is the legal age of consent and Gismore says his sexual relations with Ksenia were consensual.

As per documents of the Federal Migration Service in Russia's Kemerovo region, where Ksenia comes from, the girl was born Oct 26, 1994, and was 15 years old at the time of the sexual assaults.

Lukashevich said that the girl is currently at a children's orphanage in Georgia, where she is receiving physical and psychological treatment.

The Russian Foreign Ministry and the Russian embassy in the US are keeping a close eye on the situation.

The diplomat added that 'such a blasphemous and outrageous case calls again for the immediate conclusion of an agreement with the United States on cooperation in international adoptions.'

The United States and Russia have been negotiating an agreement on the safety of Russian children adopted by US families since 2010.

As per the latest official figures, about 60,000 children born in Russia have been adopted by families in the United States.