What Is ISIS-K, the Group Blamed for Deadly Russia Attack?

Gunmen burst into a concert hall on the outskirts of Moscow on March 22 and killed at least 137 people in the deadliest attack on Russia in more than two decades. While President Vladimir Putin pointed the finger at Ukraine, the US government said the Islamic State movement bore “sole responsibility” for the atrocity. More specifically, US officials have identified one branch known as Islamic State Khorasan, or ISIS-K. Here’s what we know about the militant group.

ISIS-K is a regional offshoot of the broader Islamic State organization, classified as a terrorist group by much of the world. ISIS-K was formed in 2014 or 2015, largely by defectors from the Afghan Taliban and Tehrik-e Taliban, a group dedicated to the overthrow of Pakistan’s government.