"FSB Director Bortnikov reported to Putin on the detention of 11 people, all four terrorists directly involved in carrying out the attack," the Kremlin said.
Further work is underway to identify the accomplices in the attack, the Kremlin added.
A shooting occurred on Friday evening in the Crocus City Hall concert venue just outside Moscow followed by a massive fire. A Sputnik correspondent who witnessed the attack reported that at least three men in camouflage burst into the music hall, shooting people point-blank and throwing incendiary bombs.