U.S. authorities have what they say is compelling evidence that Tamerlan and Dzhokhar Tsarnaev perpetrated the April 15 bombings, which left three people dead and more than 260 injured.
But the brothers, ethnic Chechens, nonetheless appear to enjoy widespread support in the North Caucasus.
In Daghestan, where the Tsarnaevs have family and are known to have briefly lived, the accusations leveled against the two brothers have been met with incredulity.
"Frankly speaking, I don't believe it," a 34-year-old man employed at a construction company, who gave his name only as Bagaudin, told RFE/RL in Daghestan’s capital, Makhachkala. "I heard an interview on the news. It looks like [one of the suspects] went to school, I'm not sure they were extremists."
Tamerlan Tsarnaev, 26, was killed in a shoot-out with police.
His younger brother Dzhokhar, 19, was later detained in Boston after a huge manhunt and hospitalized with several injuries, including a gunshot wound to the neck.
He has since been formally charged over the attack and could face the death penalty if convicted.
Their father, who lives in Makhachkala, was quick to claim his sons’ innocence and accuse the FBI of framing them -- a theory that seems to strike a chord with some local residents.
"Of course what happened in Boston was a tragic situation, it was bad, but it is unpleasant that these people are connected with Daghestan, apparently," said Magomed Magomedov, 26. "But I don't have any detailed information whether they really did it or were set up."
Another man quizzed about the Tsarnaev brothers praised them as "cool dudes."
In neighboring Chechnya, supporters are also rallying to the defense of Dzhokhar Tsarnaev. Various posters have popped up on buildings proclaiming his innocence.
"Hang in there, brother!" reads one. "Dzhokhar Tsarnaev is completely innocent," reads another poster, which links to an online petition. "We hope that President Obama will read this petition and will check more thoroughly what is happening."
More than 3,000 people have joined a support group created for Tsarnaev on vKontakte, Russia’s biggest social network.
Meanwhile, Chechnya’s top Islamic militant group, the Caucasus Emirate, has denied involvement in the Boston bombings. Instead, it suggests that Russia’s secret services may have had a hand in the attack.