MOSCOW - Russia expressed "serious worry" Wednesday over the fate of a Russian boy adopted by an American woman who did not reveal that she is a lesbian, Moscow's latest broadside in a growing war of words over adoption.

The ministry's human rights envoy Konstantin Dolgov said the situation in which the boy was placed under his new American family subjected him to conditions "harmful to his psychological health".

The statement by Moscow is the second this week concerning the fate of a Russian child and comes two days after Russian authorities accused a Texas couple of murdering three-year-old Maksim Kuzmin.

In the latest case of alleged mistreatment of Russian adoptees, the Russian foreign ministry accused a US woman of bringing a Russian boy into a lesbian partnership.

The woman, identified in Russian as Marcia Ann Brandt, was "living in a same-sex marriage with a Beth Chapman," but chose to hide this information when she adopted Yegor Shatabalov in 2007, said Dolgov.

Unlike some US states, Russia does not recognise same-sex marriages.

When the two women broke up in 2009, they began a legal battle over the custody of Yegor, Dolgov said in a statement.

"He was sucked into an argument over a relationship that was quite dubious from the moral point of view," he said.

"We believe that Yegor's situation is unacceptable and harmful to his psychological health," he said, adding that the San Francisco consulate was not granted access to the boy.

Russia has long complained about the treatment of Russian orphans adopted by American parents and in December controversially passed a law banning adoptions of Russian children by Americans.