South African police fired stun grenades, rubber bullets and teargas to break up students protesting for free education in Johannesburg with protesters retaliating by throwing rocks at police cars.

Protesters earlier gathered at Johannesburg’s Wits University as students prepared to return to class before officers moved in to enforce a ban on public gatherings.

Two students were arrested and another and one staff member were injured in the violence on Tuesday at the University of the Witwatersrand, or Wits.

Similar unrest has occurred since last month at other financially struggling South African universities, forcing a number, including Wits, to close.

The university sought to re-open on Tuesday; the main campus was disrupted, but classes proceeded on other Wits campuses.

Protesters said they want free university education to help close South Africa’s inequality gap, which is still largely divided along colour lines.

Two students were also arrested at the University of Cape Town, where protesters tried to block entrances and disrupt lectures, said Max Price, the vice-chancellor. However, he said, most operations proceeded at the university, which had also been shut because of demonstrations.

Last year, students – many of them so-called “born frees”, who grew up after apartheid – staged a series of huge demonstrations that forced the government to abandon planned fee increases for 2016.

Funding for South Africa’s universities has been stretched as the economy endures flatlining growth and the government struggles with a 27 percent unemployment rate.

Student activism played a central role in the fight against apartheid, with the massacre of pupils in Soweto by white police officers in 1976 seen as a key date in the country’s tumultuous history.