A bomb targeting Greece's National Economy Ministry shattered windows and damaged cars in Athens' main square early Monday, injuring three people, police said.

Authorities said the bomb, detonated by a timer, was apparently hidden in a container on the back of a stolen motorcycle at the central Syntagma Square.

There was no claim of responsibility, but the blast — the second targeting a ministry this year — raised fears of renewed violence by far-left militant groups that plagued Greece in the 1980s and part of the '90s.

Syntagma Square is one of Athens' busiest areas and the center of the city's Christmas and New Year's celebrations.

The caller said the nearby National Economy Ministry — which suffered limited damage — had been the intended target.

Three people were hospitalized with cuts.

Monday's bombing coincided with labor protests against Greece's conservative government and the trial of 15 members of a deadly terrorist group, November 17, which is blamed for 23 killings and dozens of bombings between 1975 and 2000.

In June, Greece's Labor Ministry was the target of an overnight bomb attack, but no one was injured. A previously unknown group calling itself Revolutionary Struggle claimed responsibility.