Platinum prices surged after South African authorities on Thursday killed an undetermined number of miners protesting at a massive platinum mine northwest of Johannesburg.

Authorities opened fire on strikers, killing an undetermined number, who have been protesting at Lonmin PLC's massive Marikana mine, Reuters said. Estimates of fatalities ranged from a handful to nearly 20.

The illegal strike and associated violence reportedly stems from a rivalry between two unions, the more established National Union of Mineworkers, which opposes the strike, and its Marxist rival, Association of Mineworkers and Construction Union.

London-based Lonmin, which said its losses from the now six-day old protests, have risen to the equivalent of 15,000 ounces of platinum, closed all its South African operations. The company is the world's third-largest platinum producer and accounts for about 12 percent of global platinum supply.

The most actively traded platinum in New York jumped 3 percent to $1,440.70 in afternoon trading.