Russia launched a terrorism probe on Wednesday after a 17-year-old student blew himself up at regional headquarters of the FSB security agency, wounding three employees.
Several minutes before the suicide blast in the northern city of Arkhangelsk, a post on an anarchist forum warned of an imminent explosion.
Investigators said they were checking whether the suspected bomber was a member of any banned organisations.
An explosive device detonated in the FSB building shortly before 9.00am local time, authorities said.
Investigators identified the bomber as a 17-year-old local resident.
An official, who spoke to AFP on condition of anonymity, named the suicide bomber as Mikhail Zhlobitsky, a student at a local technical college.