A powerful bomb damaged a bank in Athens early on Tuesday but caused no injuries, police said.
The bomb, placed outside the Greek bank Eurobank in the southeastern Argyroupoli district, was the latest in a string of attacks that have rocked the Greek capital in recent months.
"We believe it is a terrorist attack, the anti-terrorism squad is investigating the remnants of the bomb and the area," said a police source who declined to be named.
Greece has suffered a string of anarchist and leftist bombing and arson attacks aimed at domestic and foreign firms since widespread rioting in December that was provoked by the police killing of a teenager.
An unidentified caller warned a Greek newspaper about Tuesday's attack about 10 minutes before the bomb exploded, the police source added.