Students were attending lectures on the ground floor when the bomb exploded in a second-floor bathroom of the mechanical engineering department. Other students had been evacuated after an anonymous caller warned of the bomb 20 minutes before the blast.
No group has claimed responsibility.
The attack, in downtown Athens, came days before the 23rd anniversary of a bloody student uprising that felled the military junta that had ruled Greece between 1967 and 1974.
Annual celebrations, featuring mass rallies at the U.S. Embassy, usually end in late-night clashes between police and self-proclaimed anarchists.
Last year, youths vandalized the Polytechnic University and hurled hundreds of gasoline bombs at police during a 24-hour siege of the campus. Police arrested 504 people. In 1991, the university was also the battleground for riots following anniversary celebrations.
Army patrols set out yesterday morning for the Huanca mine, 480 miles southeast of Lima, which caved in during Tuesday's magnitude-6.4 quake. They navigated roads blocked by landslides and washed out by recent flooding.
The quake did the most damage to Nazca, a town of 25,000, and nearby small towns.