The explosion occurred near the regional department of the Emergency Situations Ministry.
In Vladikavkaz, capital of Russia's North Ossetia, another bomb exploded early this morning causing damage to a communications-transmission tower.
Both regions are near Chechnya, where Russian forces have been battling militants.
The Chechnya Conflict
The aftermath of a December 2002 Chechen resistance attack on the main government building in Grozny (epa)