A 29-year-old man was in the hospital on Monday after being knifed in central Thessaloniki on Sunday night during an event in the northern city commemorating the Pontic genocide, the systematic killing of ethnic Greeks by the Turks during World War I.
The attackers are believed to belong to anti-establishment groups.
According to the news website thestival.gr, the 29-year-old was chased by four assailants and sought refuge in a branch of the gaming firm OPAP.
The assailants reportedly cornered him there and knifed him four times - three in the back and one in the arm.
Officers of the police's motorcycle-riding DIAS unit immediately arrested two of the four attackers who were positively identified by the victim.
Police were using footage from the shop's closed circuit television camera to try and identify the other two assailants.
According to police sources, the 29-year-old was known among anarchist circles for his participation in rallies in the northern city protesting Greece's name deal with what is now North Macedonia.