Moscow, Apr 26 (IANS/RIA Novosti): Russian President Vladimir Putin has accused the US of attempting to prove it was "the toughest" by adopting a law introducing sanctions against Russian officials suspected of human rights abuses.

Speaking at a live question-answer session with the Russian public, Putin said the adoption by the US late last year of the Magnitsky Act, named after a whistleblowing Muscovite lawyer who died in police custody in 2009, was evidence of Washington's "imperial behaviour".

"Why was this done?" Putin said. "To show 'we are the toughest here'. This is imperial behaviour."

Russia responded to the law with tit-for-tat sanctions against US officials, as well as a controversial ban on American families adopting Russian children.

"We warned them we would respond," Putin said.

The Russian leader admitted a "cooling off" in Russia's recent relations with the US, but said ties had begun to worsen after the US-led invasion of Iraq in 2003.

"We observe chaos everywhere and do not believe that the US position is undoubtedly correct," Putin added. "But this does not mean we do not need to straighten out relations with them."