The U.S. State Department expressed concern on Wednesday over reports that South African riot police had fired stun grenades at hundreds of students protesting tuition increases.

State Department spokesman John Kirby told reporters at a briefing that the agency had seen the reports and would closely monitor the situation. "Obviously our position ... in terms of the right of peaceful protest remains the same," he said.

The protests, some violent, have disrupted at least 14 of South Africa's universities in the past week. At issue is a proposed 11.5 percent tuition increase.

Riot police fired stun grenades as hundreds of students stormed the parliament precinct in Cape Town to disrupt the reading of Finance Minister Nhlanhla Nene's interim budget.

The protesters have rejected a proposal by some student leaders and government officials to cap fee increases at 6 percent for 2016, just above inflation.