One person was killed and three others wounded in an explosion on Wednesday at a branch of Russian intelligence in Arkhangelsk, north of the country.
The blast occurred before 9 am local time in the intelligence building in the city center, said provincial governor Arteom Boutigin.
The governor of the region, Igor Orlov, it is too early to talk about a suicide bombing, according to AFP.
"The situation is very serious," Orlov said, adding that the authorities were trying to identify the dead person and the type of explosive device.
"We are imposing measures to enhance the security of all government and official buildings in the Arkhangelsk region," about 1,000 kilometers from Moscow.
The governor also inspected the location of the blast while the intelligence services held an emergency meeting.
