ATHENS, Greece (AP) -- A bomb targeting Greece's National Economy Ministry shattered windows and damaged cars in Athens' main square early Monday, slightly injuring three people, police said.
Authorities said the bomb, which detonated by a timer, was apparently hidden in a container on the back of a motorcycle at the central Syntagma Square, and exploded outside a central post office.
The blast occurred at 6:10 a.m. (0410GMT), shortly after an Athens newspaper received two phone calls warning of an attack.
The caller said the nearby National Economy Ministry -- which suffered limited damage -- had been the intended target. He did not identify any group behind the explosion or the reason for the attack.
Monday's bombing coincided with the start of strikes by Greece's largest unions against plans by the conservative government to change labor rules across the public sector.
Syntagma Square is one of Athens' busiest areas and the center of the city's Christmas and New Year's celebrations.