A bomb exploded near the Acropolis in central Athens on Wednesday night, causing damage but no injuries.
Police told Reuters the blast happened outside the house of ship owner Nikos Tsakos, who until recently sat on the board of the Bank of Cyprus, Greece's biggest lender.
The force of the explosion shattered windows.
A newspaper received a warning phone call about half an hour before the explosion at 8:30 p.m. local time.
No one has claimed responsibility for the bomb, the Washington Post reported.
Reuters described the bomb as "makeshift" and police spokesman Panagiotis Papapetropoulos said "judging by the minor extent of the damage, it can't have been a very strong explosive device."
There has been a series of bomb attacks in debt-stricken Greece, which is in its sixth year of recession.
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Government austerity measures in exchange for financial aid from the European Union and International Monetary Fund have angered many Greeks.