Russia insists that it is not going to talk to Mr Maskhadov, because he does not "control the situation" in the republic - a claim the Chechen president rejects.

BBC: Defiant Maskhadov warns Moscow

They are thought to have lived in Kyrgyzstan, a Central Asian republic which is home to many Chechen refugees who were deported under Stalin.

BBC: Profile: Dzhokhar and Tamerlan Tsarnaev

Though he is ethnically Chechen, Anzor Tsarnaev grew up in the former Soviet republic of Kyrgyzstan because his parents were deported there in the Stalin era alongside many other ethnic Chechens.

WSJ: Russia Distances Itself From Chechen Brothers

The ethnic Chechen family came to this country in 2002, after fleeing troubles in Kyrgyzstan and then Dagestan, a predominantly Muslim republic in Russia's North Caucasus.

NPR: For Bombing Suspects, Question May Be Who Led Whom