President Vladimir Putin yesterday signed a law that bans Americans from adopting Russian children and imposes other sanctions in retaliation for a new US human rights law that he says is poisoning relations.

Washington has called the new Russian law misguided, saying it ties the fate of children to "unrelated political considerations", and analysts say it is likely to deepen a chill in US-Russia relations and harm Putin's image abroad.

Six children whose adoption has already been decided in court will go to the US, while 46 children whose adoption was still underway must stay in Russia, Putin's spokesman Dmitry Peskov told Dozhd television channel.

The new law, which has also ignited outrage among Russian liberals and child rights' advocates, takes effect on January 1.

The legislation will also outlaw some non-governmental organisations that receive US funding and impose a visa ban and asset freeze on Americans accused of violating the rights of Russians abroad.

Pro-Kremlin legislators initially drafted the bill to mirror the US Magnitsky Act, which bars entry to Russians accused of involvement in the death in custody of anti-corruption lawyer Sergei Magnitsky and other alleged rights abuses.

The restrictions on adoptions and non-profit groups were added to the legislation later, going beyond a tit-for-tat move and escalating a dispute with Washington at a time when ties are already strained by issues such as the Syrian crisis.

US-based human rights organisation Freedom House called the law an "attack against one of the most vulnerable groups in the Russian society."

The adoption ban may further tarnish Putin's international standing at a time when the former KGB officer is under scrutiny over what critics say is a crackdown on dissent since he returned to the Kremlin for a third term in May.

Seeking to dampen criticism, Putin also signed a decree ordering an improvement in care for orphans.

Critics of the Russian legislation say Putin has held the welfare of children trapped in a crowded and troubled orphanage system hostage to political manoeuvring.

Russian orphanages are woefully overcrowded and that adoptions by Russian families remain modest, with some 7,400 adoptions in 2011 compared with 3,400 adoptions of Russian children by families abroad.

More than 650,000 children are considered orphans in Russia. Of those, 110,000 lived in state institutions in 2011, according to government figures.-Reuters