– Gunmen attacked a concert hall outside Moscow, killing 137 people
– The U.S. and other Western countries warned of an imminent attack in Moscow, linked to Islamic State
– Russia accused Ukraine of being involved in the attack, which Ukraine denied
– Four suspects, citizens of Tajikistan, were charged with terrorism in connection to the attack
– France raised its security alert, linking the attack to Islamic State
– The U.S. and Russia traded accusations over the attack, with the U.S. denying any Ukrainian involvement and Russia questioning U.S. assertions