A bomb exploded outside the offices of a Greek business federation in central Athens early on Tuesday, police officials said, smashing windows but causing no injuries.<br />Attacks against banks, politicians, journalists and businesspeople are not uncommon in Greece, which has a long history of political violence and has been mired in its worst economic crisis in decades.<br />Tuesday's blast, which police believe was carried out by domestic guerrilla groups, is the first such attack since leftist Prime Minister Alexis Tsipras came to power in January.<br />The device, triggered by a timer and placed in a backpack near the entrance of the Hellenic Business Federation offices, went off around 3:30 a.m. .<br />An anonymous caller warned a newspaper some 30 minutes earlier, a police official said on condition of anonymity.
