An incendiary device went off outside an Interior Ministry building early on Saturday but only caused minor damage and no injuries, police said.
The device, which was made from camping gas canisters, exploded at about 5.30 a.m. outside the building housing the Information Society Department in the Hymettus area for Athens.
Nobody claimed responsibility for the attack.
Assailants also started a small fire outside a house in Agrinio, central Greece, belonging to the family of PASOK MP Sophia Giannaka.
No major damage was caused.