A senior Russian official said on Tuesday that the Boston Marathon bombings could have been prevented if American officials had followed through with Russian intelligence.
Officials previously hewed to President Vladimir Putin's statement that Russia had no information that could have prevented the attacks.
"The Russian side warned the American side about the Tsarnaev brothers, but this information was not taken seriously by the American side, which is what led to that tragedy," Valentina Matvienko, the speaker of Russia's senate, said on Tuesday, referring to suspects Tamerlan and Dzhokhar Tsarnaev, the Interfax news agency reported.
Matvienko made the remarks after a meeting with Britain's ambassador to Russia. She is the longtime governor of Putin's hometown of St Petersburg, is considered a close Kremlin confidante and was named Russia's most powerful woman this year by Ekho Moskvy radio.
"Today the world has to deal with common global challenges and international terrorism, as well as crime, and the cooperation of intelligence services becomes extremely significant for this issue," she added.
Russia told the FBI in 2011 that Tamerlan Tsarnaev had plans to join insurgents in Chechnya. The agency did a cursory investigation and closed its assessment on Tsarnaev.
Security officials told a Congressional delegation to Russia last week that they believed that if Russia and the US had worked together more closely, the bombings might have been averted, Rep William Keating said on Friday.
He added that a top Russian counterintelligence official told the delegation that "had we had the same level of communication as we do now, the Boston bombing may never have happened."
It was unclear, however, whether the Russians said they had enough information to prevent the attack at the time. Rep Steve Cohen said on Sunday that Russian officials seemed not to have known that Tamerlan Tsarnaev went to Dagestan, a restive Caucasus province racked by an insurgency, for six months last year when he returned to Russia.