The bomb exploded outside the building of the Hellenic Federation of Enterprises in the center of the Greek capital early on Tuesday, police officials said.

The front of the building was damaged, but no one was hurt, the Athens-Macedonian News Agency reported.

The explosive device, concealed in a backpack, was triggered by a timer.

The area near Athens' main Syntagma Square where the blast took place had already been cordoned off by police after two newspapers received telephone tip-offs from an indentified man.

Bomb disposal squads have been examining the scene, which is located in close proximity to parliament.

History of attacks

Greece has a long history of political violence, with bank, politicians, journalists and businesspeople being the most common targets of attacks that are mostly carried out by militant anarchist and far-left groups.

The number of attacks has increased since 2010, when Greece first introduced harsh austerity measures in exchange for international bailouts.

Tuesday's blast is the first such attack since left-wing Prime Minister Alexis Tsipras came to power in January, vowing to get rid of the measures. In July, however, Athens agreed to a third bailout that entails further austerity for the debt-stricken country.

tj/kms (Reuters, AP, dpa)