A bomb has exploded outside the offices of Greece's industry association in the capital Athens, causing damage but no injuries, police say.

The bomb, placed in a backpack near the entrance of the Hellenic Business Federation offices near the busy Syntagma square, went off at around 3.30 a.m. local time (1.30 am GMT) on Tuesday.

The blast smashed windows of the building, which is across from Athens' top hotels and adjacent to the embassy of Cyprus.

Police cordoned off a two-block area surrounding the building and bomb disposal squads examined the scene.

Sources said that telephone calls had been made to two Athens daily newspapers at 0050 GMT, warning police of the attack against the building.

The police quickly ruled out a possible terrorist connection, saying that the warning before the attack and the target chosen showed it was likely a far-left domestic group.

Attacks against banks, politicians, journalists and business people are not uncommon in Greece, where many of them are blamed on militant anarchists and far-left groups in the country.