By William Pfaff

Johannesburg, South Africa

Police opened fire on armed striking miners in South Africa's North West province killing at least a dozen people.

The shooting followed failed attempts by the police to disarm and disperse some 3,000 rock drillers belonging to the militant union Association of Mineworkers and Construction Union (AMCU).

The strikers, who were demanding $1,500 increase in monthly wage, were gathered in a hilltop overlooking the Marikana mines, the world's third largest platinum mine. They were holding clubs, spears and machetes.

After the police fired tear gas and water cannons to disperse them, police said someone fired from the crowd prompting them to shoot back, according to the South African news site Fin24.com. The shooting lasted two minutes after which witnesses saw at least a dozen people sprawled on the ground.

Another news report cited witnesses as saying the strikers threw firebombs or grenades at the police forcing the latter to fire at them.

Reacting to the shooting incident, South African President Jacob Zuma called on the strikers and the company to prevent the situation from deteriorating. Zuma also offered condolence to the families of the dead victims.

Political parties, including the ruling African National Congress, called for an investigation of the shooting.

The shooting was the latest violence to mark the AMCU strike that started Friday. On Monday, strikers clashed with police and stole several firearms from officers. The guns were then used to shoot two officers dead. One mine worker was also shot dead.

Prior to this week's violent confrontation between police and strikers, AMCU workers clashed with workers from another union, the National Union of Mineworkers, over recruitment competition.

Lonmin Plc., the sole Marikana mine operator, gave the strikers until Friday to return to work so other non-striking workers keeping away from the mines to avoid harm can also return to work. Company officials said the strike has caused the loss of 15,000 troy ounces of platinum output and they fear missing the full-year production target of 750,000 ounces.

South Africa accounts for 80 percent of the world's platinum production.

World - Police Dispersal of Striking Miners in South Africa Kills at Least a Dozen | News of the World