At least 30 people were killed when police clashed with striking miners at South Africa's Marikana mine on Thursday.
According to witnesses, police opened fire on strikers armed mostly with clubs and machetes.
The platinum mine owned by Lonmin has been at the centre of a violent pay dispute, exacerbated by tensions between the National Union of Mineworkers and the Association of Mineworkers and Construction Union.
The AMCU also wants a pay rise of 12,000 rand ($US1500) per month.
Violence during the strike had already killed 10 people.
Speaking on local radio, police minister Nathi Mthethwa confirmed the death toll and said many people were injured and the number keeps going up.
The incident is one of the bloodiest police operations since the end of the apartheid in South Africa.
Police were sent to intervene after several thousand miners gathered at Marikana, about 100km north-west of Johannesburg, to call for a pay rise of 12,000 rand ($US1500) per month.
The circumstances that led police to open fire remain unclear, but reports from eyewitnesses suggest the shooting took place after a group of demonstrators rushed at a line of police officers.
Witnesses said missiles - thought to be either petrol bombs or grenades - were thrown at the police, who responded by opening fire.
One witness, Molaole Montsho, of the South African news agency Sapa, said police had first used water cannon, tear gas and stun grenades in an attempt to break up the protest.
Lonmin said in a statement on Thursday that any strikers who did not return to work by Friday would be sacked. The company said it has missed six days of production as a result of the unrest.