Hundreds of students demanding free education have clashed with police in renewed violence at South Africa's top university in Johannesburg after it attempted to reopen following recent unrest. Police used tear gas, rubber bullets, stun grenades and water cannon on Monday to disperse stone-throwing protesters at Witwatersrand University, also known as Wits. Blade Nzimande, the country's education minister, appealed for dialogue and condemned the violence, saying the university's efforts to run its academic programme were being "held at ransom by irresponsible and disrespectful striking students". Two arrests were made and minor injuries reported, according to a statement by the university. "The students started throwing sizeable rocks that could have maimed or killed people," Wits said in a statement after trying to reopen on Monday.