The FSB detained a man who had taken part in preparing to set governmental offices on fire and attack law enforcement agents.
"A Russian citizen born in 2001, who was involved in the preparation of arson of government buildings, armed attacks on law enforcement officials and public servants, was detained," the Russian Federal Security Service said in a statment.
A Makarov pistol with improvised ammunition, three Molotov cocktails, knives and diaries with information about a planned crime were confiscated from a detainee.
The FSB did not specify what motives the detainee had.