South African riot police opened fire on striking miners armed with machetes and sticks at Lonmin's Marikana platinum mine, killing at least a dozen men in the deadliest episode of a week of union violence. Heavily armed officers backed by armored vehicles were laying out barbed wire barricades when they were outflanked by some of the estimated 3,000 miners massed on a rocky outcrop near the mine. Police opened fire with automatic weapons on a group of men who burst out from behind a vehicle. The volley of bullets threw up clouds of dust, which cleared to reveal at least seven bodies lying on the ground. It was not clear whether the police were fired upon. They appeared to be on edge and with rifles pointing forwards immediately before the incident. Reuters photographs showed spears and clubs lying near the bodies. The SAPA domestic news agency said one of its reporters had counted 18 bodies near a squatter camp close to the mine, Lonmin's flagship platinum plant, which was forced to shut down on Tuesday because of the union unrest. There has been no confirmation the death toll.