Russian prosecutors asked a regional court Thursday to annul the adoption and bring home from the United States a young boy whose brother died in Texas leading to a new flare-up in tensions with Washington.
The request comes after Russia late last year banned all adoptions by American parents, a measure that came in reprisal for US legislation that targets Russian officials deemed to have committed rights abuses.
Tensions flared again this week over the January death in Texas of a three-year-old adopted boy, Maxim Kuzmin, with Russian investigators saying he was murdered by his new American mother.
The Texas couple that adopted Maxim Kuzmin known under his American name Max Shatto is also raising his younger brother Kirill.
"According to existing information, Kirill's stay with the adoptive family may put at risk his life and health," the General Prosecutor's Office said in a statement.
Prosecutors from the Pskov region in northwestern Russia, which was home to the two boys, have filed a lawsuit against their adoptive US parents, Alan and Laura Shatto, with a regional Pskov court, the statement said.
They say the boy should be brought back to Russia with a view to finding him Russian parents or returning him to his biological mother.
Asked whether it was possible to bring back the already adopted child, a spokeswoman for regional prosecutors, Yaroslava Tarakanova, told AFP that it would be up to the court to determine that.
Some officials have recently raised the prospect of Russia banning all foreign adoptions in the future and even bringing back home Russian children already living in the United States.
The Russian foreign ministry expressed "serious worry" on Wednesday over the fate of another Russian boy adopted by an American woman who did not reveal she was a lesbian.
The biological mother of the boys adopted in Texas, Yulia Kuzmina, who had been stripped of her parental rights, told Russian state television this week she wanted her son back.
The probe into the death of his brother was opened after the Kremlin children's ombudsman Pavel Astakhov said on Twitter this week that the three-year-old boy had been killed after being given strong psychoactive drugs.
-- 'The US is not ready for dialogue' --
The controversial issue of adoptions led the US ambassador to Moscow Michael McFaul and a top Russian lawmaker to trade verbal blows earlier Thursday.
The emotionally charged exchange came after McFaul refused to show up in the Russian parliament's lower house to answer questions about recent deaths of Russian children in the United States.
"By refusing to come to the State Duma to discuss the deaths of our children the US ambassador has shown that they are not ready for a serious dialogue on this problem," Alexei Pushkov, the head of the Duma committee on international affairs, wrote on Twitter.
McFaul countered that he was "always happy" to meet Russian officials to discuss adoptions but would not do so in parliament.
"As a norm, US ambassadors do not participate in hearings of foreign parliaments," he tweeted. "Do Russian ambassadors?"
Maxim Kuzmin's death will be among key topics of a meeting between Russian Foreign Minister Sergei Lavrov and new US Secretary of State John Kerry, the foreign ministry's rights envoy Konstantin Dolgov said Thursday.
The meeting is set to take place on February 26 in Berlin.
If the ongoing investigation proves that the US parents murdered their adoptive Russian son, they should be severely punished, Dolgov said in comments posted on the website of the ruling United Russia party.
The head of the Investigative Committee, Alexander Bastrykin, said that 21 Russian children had died in the United States in recent years, and in ten of those cases American parents were being prosecuted at home.
Russia has opened criminal probes into the deaths of another seven children, Bastrykin said.