A leading Russian politician and supporter of President Vladimir Putin has denied a report that he adopted an infant who had been forcibly taken from an orphanage in Ukraine.

Citing Russian and Ukrainian documents, the BBC reported on Thursday that Russian lawmaker Sergei Mironov had adopted a child, now two years old, who was taken from an orphanage in the Ukrainian city of Kherson last year.

Russia has been accused of forcibly deporting thousands of Ukrainian children from schools, hospitals and orphanages in parts of the country controlled by its forces.

The International Criminal Court (ICC) has issued an arrest warrant for Putin and his children's commissioner for "the war crime of unlawful deportation ... and transfer" of children from Ukraine to Russia.

According to the BBC, Mironov was "named on the adoption record of a two-year-old girl who was taken in 2022 by a woman he is now married to."

Mironov on Thursday called the investigation a "hysteric fake unleashed by Ukrainian special services and their Western curators."

Without commenting on the specific details of the BBC report, he said it was an "information attack" designed to "discredit" him.

Mironov, 70, leads a pro-Kremlin opposition party in Russia's parliament.

He previously spent a decade as head of the Federation Council, Russia's upper house of parliament – a key post marshalling the Kremlin's legislative agenda.

He is a staunch supporter of the military campaign against Ukraine, and has been awarded honours by Putin for his service to Russia.

In his response on Thursday, Mironov said Russia would achieve "complete victory" against Ukraine on the battlefield.

The BBC reported the child he allegedly adopted, whose original name is Margarita, had her identity changed after being taken to Russia.

She was one of 48 children who went missing from the Kherson Regional Orphanage after Russian forces seized the southern city.

Ukraine regained control of Kherson last November after Moscow's forces were forced into an embarrassing retreat.

Kyiv says it has identified around 20,000 children that were taken to Russia after its forces launched a full-scale military campaign in February 2022.

Fewer than 400 have been returned.

Moscow has not denied transferring thousands of Ukrainian children to Russia, but claims it did so for their own protection. (AFP)