Moscow attack explainer: Why would Islamic State attack Russia and what will Putin’s response be?

After IS claimed responsibility for shooting in Moscow’s Crocus city hall, questions remain about how Russia will respond

A man places flowers at a spontaneous memorial in memory of the victims of the Moscow attack. Picture: AP Photo/Dmitri Lovetsky

The attack on Moscow’s Crocus City concert hall is the deadliest attack claimed by the Islamic State (IS) on European soil, with 137 people confirmed to have been killed.

On Friday evening, attackers carrying assault rifles entered the concert hall on the outskirts of Moscow, shooting for nearly an hour as panicked concertgoers scrambled to escape. Then the attackers set the venue on fire.