A bomb hidden on a parked motorcycle has exploded outside two court buildings in central Athens, damaging cars and shattering windows but leaving no one hurt, officials said.
The blast occurred following a warning telephone call to a newspaper and private TV station, authorities said. Authorities evacuated the targeted buildings.
There was no immediate claim of responsibility, but suspicion fell on Greek militant groups, which have stepped up attacks in the past two years. A group of suspects is facing trial next month.
The blast shattered windows and nearby shop fronts, damaged cars and sent up a cloud of smoke that was visible across the city.
At least a dozen suspected members of the violent anarchist group calling itself Conspiracy Nuclei of Fire are due to go on trial on January 17. The group claimed responsibility for a spate of parcel bomb attacks targeting embassies in Athens and other sites in November.
A violent Italian anarchist group carried out a string of embassy bombings in the past week, in solidarity with jailed Greek militants.