A powerful bomb exploded outside an Athens tax office early today causing considerable damage but no injury, Greek police said.
The blast occurred at 4.35am local time today in the central Ambelokipi district, and followed an anonymous warning call to two Athens newspapers, a police spokeswoman said.
Magdalini Bakalarou said the bomb "caused serious damage" in an area between the tax office and a nearby McDonalds building.
There has been no immediate claim of responsibility for the bombing.
Last month, a far-left militant group called Armed Revolutionary Action said it carried out a similar attack on another Athens tax office that caused no injury.
Greek militants have stepped up attacks in recent months, following December's fatal police shooting of a teenager that sparked Greece's worst rioting in decades.
In the bloodiest incident, gunmen shot dead an anti-terrorist officer guarding a witness in Athens on June 17. A group called Sect of Revolutionaries, which emerged shortly after the riots, has claimed responsibility for the shooting.
Also early today, suspected anarchist arsonists set off a small incendiary device outside an immigration policy centre in central Athens, causing damage but no injury.