The SITE Intelligence Group American consultancy organization claims that the Islamic State has “revealed the four fighters involved in the Moscow concert hall operation” and is “boasting” about its “fiercest attack in years.” https://ent.siteintelgroup.com/Jihadist-Threat-Statements/is-reveals-4-fighters-involved-in-moscow-concert-hall-attack-boasts-fiercest-attack-in-years.html