The death toll rises to 115 in an attack on a Moscow concert hall

Russian officials say the death toll has risen to 115 in an attack by assailants who burst into a concert hall and sprayed the crowd with gunfire.

The Islamic State group has claimed responsibility for Friday's attack in a statement. The attack was the deadliest in Russia in years and left the concert hall in flames with a collapsing roof.

The head of Russia's Federal Security Service told President Vladimir Putin on Saturday that four people directly involved in the attack were among 11 detained, Russian state news agency Tass said.