The Tsarnaev brothers come from a Chechen family which once lived in the Russian region of Dagestan where the authorities are battling an Islamist insurgency.
Experts in the US are playing down a possible link to the Caucasus but some in Russia believe their origins may be significant.
Konstantin Zatoulin, Director of the Institute of CIS Countries (Russia’s Commonwealth of Independent States of former Soviet Republics) told euronews:
“In the North Caucasus there are more than a few bombs exploding there time after time. It seems to me that if there is really a trace of Caucasus terrorism, which cannot be excluded completely, then this is an occasion for the United States to reflect whether they acted correctly before – and whether they act correctly now when they give (people from there) opportunities to speak, and when they give asylum to those who are known for their pathological hatred for Russia”.
The elder Tsarnaev brother is said to have visited Russia last year; unconfirmed reports link him to extremist material on the internet.
US investigators will be examining every detail of the suspects’ backgrounds.