It was not immediately clear who fired the first shots in a shoot-out on Thursday between police and strikers at Lonmin's mine in Marikana in the North West.
The shooting erupted when police sought to disperse armed, striking workers who had gathered on a hill, in the area that had already seen 10 deaths in violent protests the past week.
After a call for the miners to disarm themselves, the group - singing and hitting their spears against pangas - starting moving down the hill to a nearby informal settlement.
The police tried to intercept them using water cannons, tear gas and stun grenades.
The workers started running in different directions, some heading for the open veld and others toward the informal settlement.
A Sapa reporter on the scene said gunshots could be heard from the police, which lasted for three minutes.
Police on the scene said workers shot at them first before they opened fire. The shooting left at least 18 people dead or wounded. They were seen lying on the ground.
Police were not immediately available to comment on the number of dead and wounded in Thursday's shooting.
An uneasy calm returned to the Marikana mine area on Thursday evening as paramedics attended to those who were hit.
Policemen involved in the shooting were returning to their bases as two helicopters circled the area around the hill where the strikers had gathered.
Those who already died in violent protests at the mine included two security guards and two police officers. - Sapa