A bomb exploded outside Citibank branch in northern Athens suburb around 3 a.m. local time Monday, damaging the parked cars nearby, but no injuries were reported, local radio reported.
Police said they haven't received warning call and there was no claim of responsibility for the attack.
Since a 15-year-old boy killed by police last December, Athens witnessed a series of protests and bomb attacks which aroused the worst riots in the country for decades. On February 18, police in Athens defused a "powerful" makeshift time bomb outside the Greek headquarters of US banking group Citibank.
Banks in Greece are routinely targeted by suspected anarchist groups that usually employ Molotov cocktails and gas canister bombs.
In the last month, there were a spate of arson attacks in Athens and Thessaloniki against newspaper offices, senior justice officials, a university professor and a prominent opposition politician.
Local media reported that four hooded men opened fire at cars parked outside a Greek television station in Athens before fleeing on motorbikes last February. The station is run by a publisher who also owns a newspaper hit in last month's attacks.