Tensions were high at one of South Africa\'s biggest platinum mines a day after police opened fire on machete-wielding striking workers, killing as many as 18. South African President Jacob Zuma said he was \"shocked and dismayed by this senseless violence.\" \"I have instructed law-enforcement agencies to do everything possible to bring the situation under control and to bring the perpetrators of violence to book,\" he said in a statement. Some South Africans expressed horror at the shootings, with some comparing them to the apartheid era of racial segregation when white security forces used live ammunition against black township protesters. Police spokesman Capt. Dennis Adriao told reporters officers did their best to handle a volatile situation, and accused the miners of opening fire first. The bloodshed after several days of violence occurred at a troubled Marikana mine in Rustenburg, about 60 miles northwest of Johannesburg, owned by London\'s Lonmin PLC, the world\'s third-largest platinum producer. Rustenburg was a host city of the 2010 FIFA World Cup men\'s national soccer tournament. About 3,000 rock drillers have been on strike for a week, demanding their wages double as part of a battle between two unions seeking to represent them. Several hours before the violence, Lonmin warned the miners in a statement the strike was illegal and any worker who did not return to work Friday would be fired. Police tried unsuccessfully to disperse protesting workers camped out near the mine, police and a miners\' union said. Angry miners -- who the Johannesburg Mail & Guardian reported were \"chanting war songs\" and carrying sharp dead fish known as pangas among their weapons -- attacked police first, police said. Footage shown on South Africa\'s 24-hour eNews Channel showed police approaching the weapons-carrying protesters and firing tear gas into the crowd. Gunfire followed. The footage showed several bodies lying motionless. It wasn\'t immediately clear what type of ammunition police used. Twelve miners were killed, eNews said. The South African Press Association reported 18 dead. \"The South African Police Service was viciously attacked by the group, using a variety of weapons, including firearms,\" Adriao said. \"The police, in order to protect their own lives and in self-defense, were forced to engage the group with force.\"