Russia arrests 11 over concert hall attack, including all 4 assailants

Russia has arrested 11 people -- including all four assailants -- over Friday's deadly attack on a concert hall, Russian news agencies reported on Saturday.

The head of the FSB security service informed Russian President Vladimir Putin "about the detention of 11 people, including all four terrorists directly involved in carrying out the attack," Russian state news agencies cited the Kremlin as saying in a statement.