Twenty-four people were arrested and charged on Thursday in connection with the the violence that erupted in central Athens during a demonstration against an education bill, police said.
Officers had originally detained 52 people. The charges are not yet known.
Student protesters hurled bottles, rocks, and gasoline bombs at police which responded with tear gas. On Syntagma square about 200 protesters tried to damage the Monument to the Unknown Soldier but were pushed back by police.
More clashes followed in Propylaea later when hooded individuals hurled petrol bombs against riot police.
The protests are focused on a provision that would allow police to patrol university campuses.
The conservative government says it wants to establish a campus police force to stop university grounds from being used for illegal activities such as selling counterfeit goods or organizing violent protests.