Bombs have exploded outside Greek targets in Athens and Buenos Aires two weeks before the trial of Greek anarchists linked to a November parcel bomb campaign against foreign leaders.
No one was killed in the attacks, which caused widespread damage. In Athens a powerful device thought to be a time bomb detonated outside a court shortly after police had evacuated the area, acting on warnings delivered by anonymous callers to news media.
Some 90 minutes earlier, a firebomb had been thrown at the Greek embassy in the Argentine capital, causing material damage but no injuries, the Greek foreign ministry said in a statement.
The bomb in the Greek capital smashed windows at the Athens administrative court and at neighbouring buildings, destroying several vehicles parked outside and hurling debris over a wide area.
Another police operation was later staged across the capital in the district of Kallithea following a threatening phonecall at a local tax office but no device was found.
The government condemned the incident with spokesman George Petalotis declaring: "Those who attempt such acts will only reap condemnation from society and the state."
The bombings came two weeks before the trial of more than a dozen suspected members of a radical Greek anarchist group, Conspiracy of Fire Nuclei.
The group is held responsible for a wave of parcel bombings in November that targeted foreign embassies in Athens and European government leaders, including French President Nicolas Sarkozy, German Chancellor Angela Merkel and Italian Prime Minister Silvio Berlusconi.