The Estonian Internal Security Service is the central national security agency of the Republic of Estonia. Its primary responsibilities include protecting the constitutional order, conducting counterintelligence, and investigating specific criminal offenses. These include crimes committed by state officials, acts of terrorism, incitement to hatred, crimes against humanity, war crimes, and the illegal handling or trafficking of firearms, explosives, radioactive substances, and other strategic materials. The agency also protects state secrets and performs other internal security functions.