The suspects in the Boston Marathon bombing were identified by law enforcement officials and family members as Dzhokhar and Tamerlan Tsarnaev, ethnic Chechen brothers from Dagestan, which neighbors Chechnya in southern Russia.
They lived near Boston and had been in the U.S. for about a decade, an uncle said.
Chechnya is the home of an Islamic insurgency that has carried out deadly bombings in Russia and the region, but its militants have never been known to export violence to the West.
In the past, insurgents from Chechnya and neighboring restive provinces in the Caucasus have been involved in terror attacks in Moscow and other places in Russia.
Those raids included one in Moscow in 2002 in which a group of Chechen militants took 800 people hostage and held them for two days before special forces stormed the building, killing all 41 captors. Also killed were 129 hostages, mostly from the effects of the gas Russian forces used to subdue the attackers.
Chechen insurgents also launched a 2004 hostage-taking raid in the southern Russian town of Beslan, where they took hundreds of hostages. The siege ended in a bloodbath two days later, with more than 330 people, about half of them children, killed.
Insurgents from Chechnya and other regions also have launched a long series of bombings in Moscow and other cities in Russia.