The bomb, which was planted near the office entrance, caused structural damage to the building and shattered its windows, as well as those in a nearby apartment building. An elderly guard sustained minor injuries but was not hospitalized.
Local police have opened an investigation into the incident.
The bomb attack comes amidst rising tensions between the pro-Russian Communist Party and the ethnic Romanian nationalist opposition, which is seeking to align the country with neighboring Romania and the European Union.
Recently, opposition leaders have been organizing demonstrations calling for the resignation of the Communist-dominated Parliament and government.
In a statement read to Parliament, the Communist Party blamed the attack on "extremist elements who want to destabilize the country," according to The Associated Press.