Who are ISIS-K, the group linked to the Moscow concert hall terror attack

The State group, also known as ISIS, claimed responsibly for Friday’s deadly assault on a concert venue in Moscow, releasing graphic footage purporting to show its gunmen carrying out what was Russia’s worst terror attack in decades. Russian authorities have accused four men from the former Soviet republic of Tajikistan of being behind the attack, which left at least 137 people dead and more than 100 injured. The suspects, who are charged with committing a terrorist act and face possible life imprisonment, have been remanded into pre-trial detention through May 22 after appearing in court in Moscow on Sunday.