Police were investigating an attack on Thursday by between 10 and 15 hooded youths who entered the premises of the University of Macedonia and started smashing things using iron bars and wooden sticks.
Witnesses said members of the group also assaulted students who had been on the campus at the time, causing them minor injuries.
According to those witnesses, the assailants entered the grounds with their faces uncovered and did not initially seem suspicious.
Then they suddenly pulled on hoods, pulled out iron bars from their rucksacks and started vandalizing tables, chairs and even the university Christmas tree.
The assailants did not shout anti-antiestablishment slogans or distribute flyers with political or social messages as members of other group sometimes do.