Russia condemns all "terrorists" regardless of their nationality, President Vladimir Putin's spokesman said on Friday after US police shot dead a terror suspect who once lived in Russia.
"They all deserve to be rejected," spokesman Dmitry Peskov said, adding that Russia was awaiting official information from the US on the dead man and a suspected accomplice.
Detectives in Boston are looking further afield as they piece together their case against Marathon suspect Dzohkhar Tsarnaev.
The uncle of Boston bombing suspect Tamerlan Tsarnaev described his recent visit to Dagestan in Russia and his great shock at the attacks.
Both men were enrolled in a school in Dagestan, a neighbouring region that was drawn into Chechnya's violence during the 1990s.