The Boston marathon bomber suspects are ethnic Chechens who spent some of their childhood in Dagestan and then moved to the United States.
Chechnya and Dagestan are republics of Russia - in the country's far southwest. They are predominantly Muslim.
In the 1990s Russia fought two wars against separatist rebels in Chechnya. That increased tensions and guerilla attacks across the region.
Chechen rebels have carried out bombings and hostage-takings across Russia in recent years.
Al Jazeera's David Chater has more from Makhachkala, the capital of Dagestan, where the boys spent some of their childhood.