Expert says Moscow attack carried out by Islamic State - what videos and photos can tell us

Dr Antonio Giustozzi, a senior research fellow at the Royal United Services Institute, said the way IS carries out attacks "depends on the kind of weapons they can obtain". "So explosives, especially plastic explosives that you can use for suicide belts is not so easy to procure.... It's probably easier to procure firearms in Russia." He added the "exact choice of weapons can be dictated by what's available on the black market".