The death toll in an attack on concertgoers near Moscow has risen to more than 140 people, said Margarita Simonyan, the head of the Russian state television network Russia Today, on Saturday.

The head of Russia's Federal Security Service (FSB) reported to Russian President Vladimir Putin on the detention of 11 people, including all four gunmen suspected of being directly involved in the terrorist attack at Crocus City Hall, Russian news agencies RIA and TASS reported.

Russian authorities have initiated a criminal investigation into the attack, which the Islamic State group claimed it had carried out.