JOHANNESBURG (AP) — South African riot police fought stone-throwing students for a second consecutive day at a university campus on Tuesday amid national calls by demonstrators for free higher education.

Clashes broke out when students hurled rocks at a central building at the University of the Witwatersrand in Johannesburg and police fired rubber bullets to disperse them.

Earlier Tuesday, the university said classes had resumed despite attempts by student protesters to disrupt the academic program. On Monday, larger groups of students confronted police and campus security guards, and violence spilled into surrounding city streets.

Student protests have forced the closure of other universities in South Africa and prompted warnings that students might not be able to complete the academic year.

The government says it does not have enough money to provide free higher education and that it will cover fee increases for poor students next year. Protesters, however, say the concession does not go far enough.