Greek riot police have clashed with students protesting against a decision to close campuses in Athens on the anniversary of an uprising against military dictatorship.
Police reportedly used tear gas and stun grenades to prevent students from entering a building at Athens Polytechnic.
At least two students are said to have been seriously injured.
All colleges and universities in Athens have been locked down four days ahead of the date in 1973 when a revolt against the then junta ended in bloodshed.
Greek media say the authorities imposed the measure to prevent sit-ins.
The opposition left-wing Syriza party has accused the government of adopting a provocative, autocratic stance.
The government has accused Syriza of defending “terrorism” and lawlessness.