Now there are suspicions that Doku Umarov, the 45-year-old self-styled emir of the Russian North Caucasus, is taking the battle into Russia itself.
Until now Umarov, a veteran of Chechnya's nationalist fight with Russia, has been against killing civilians. He was critical of the Beslan attack in which Chechen rebels took 1,200 people as hostages at a school in Beslan in 2004.
In the ensuing gun battles between the rebels and Russian forces, 334 hostages were killed, more than 100 of them schoolchildren. Only one militant survived.
While he has not claimed responsibility for Monday's subway bombings, if he is behind them, it would demonstrate a change in tactics due partly, analysts suspect, to a reliance on funding to continue the fight from radical Islamists such as al Qaeda.
"It's got to the stage where the Chechens in particular are potentially looking out to the global jihad for that level of support," said Hunter.
"By aligning himself to al Qaeda or other members of global jihad it would certainly be one source of securing that funding."