MOSCOW, March 23. /TASS/. Intelligence agencies have detained 11 people, including four terrorists, who were directly involved in an attack on the Crocus City Hall, Russia’s Federal Security Service (FSB) said in a statement.

"The activities of intelligence and law enforcement agencies have resulted in the detention of 11 people, including four terrorists, who directly participated in the terrorist attack on the Crocus City Hall," the statement reads.

Work is underway to identify terrorist accomplices and establish all the circumstances of the attack.

"It has already been established that the terrorist attack was carefully planned. The weapons that the terrorists used had been placed in a cache in advance," the FSB noted.