A delegation from the governing SYRIZA party, including prominent ministers, was prevented by leftist groups from laying a wreath at the Athens Polytechnic Memorial on Friday, on the eve of the 45th anniversary of the uprising against the junta.
Television footage shows the crowd blocking the entrance of the Polytechnic campus and hurling abuse at the delegation, who were pushed away, barred from entering the building.
Some threw bottles of water and cups of coffee.
Among the delegation was Minister of Education Costas Gavroglou and the General Secretary of the party, Nikos Skourletis.
Some leftist groups accuse governing SYRIZA of abandoning its leftist roots and espousing a pro-American and pro-NATO stance.
The Hellenic Police (ELAS) are taking draconian measures regarding the anniversary events which will culminate with a rally to the U.S. Embassy on Saturday.
More than 5,000 police officers will be deployed while ELAS helicopters and drones will be monitoring activities in central Athens.
Secret police will be present in the Exarchia area next to the Polytechnic administration building.
Exarchia is the base for anarchists who traditionally attack police and vandalize the area around the Polytechnic every year on November 17.