Chechen official: Blame Boston bombers' parents, not their birthplace

Tamerlan Tsarnaev, 26, who was killed in a firefight with police, is believed to have been born in Russia near Chechnya. His brother Dzhokhar Tsarnaev, 19, is still on the run and was born in Kyrgyzstan, much farther to the east near the border with China.

The motives behind the attack that killed three people and injured 176 remain unknown. Chechnya, a Muslim enclave in the Caucasus, saw a rise in Islamist militancy when separatists fought for independence from Russia after the fall of the Soviet Union; two Chechen militants detonated bombs packed with metal nuts, bolts and screws in the Moscow subway in 2010, killing at least 40 people.

Russian President Vladimir Putin offered his help with the investigation in a condolence message to President Obama earlier this week, before the Chechen connection was known.