As a larger bomb exploded in Athens, Greece,
Separately, a small bomb that exploded outside the Greek embassy in Buenos Aires caused minimal damage overnight and no one was at the embassy, Foreign Ministry spokesman Grigoris Delavekouras told the AP.
There was no immediate claim of responsibility for either bombing, but suspicion fell on militant anarchist groups, which have stepped up attacks in the past two years. A group of suspects is facing trial in Athens next month.
Authorities in Europe and elsewhere say violent anarchist groups are showing greater international coordination. A violent Italian anarchist group carried out a string of embassy bombings in the past week in solidarity with jailed Greek militants.
There were no injuries in the Argentinian explosion, which happened at 2AM local time today.