South Africa's national police commissioner says 34 miners died and another 78 were wounded when police opened fire on striking miners outside a platinum mine, 90 kilometres northwest of Johannesburg.

Mangwashi Victoria Phiyega told a news conference Friday that her officers acted to protect their own lives after strikers armed with "dangerous weapons" charged them Thursday. She said the strikers had not dispersed earlier, despite police use of water cannon and stun grenades.

The South Africa Police Service defended the officers' actions, saying in a statement they were "viciously attacked by the group, using a variety of weapons, including firearms. The police, in order to protect their own lives and in self-defence, were forced to engage the group with force."

It was one of the worst police shootings in South Africa since the end of the apartheid era, and came as a rift deepens between the country's governing African National Congress and an impoverished electorate confronting massive unemployment and growing poverty and inequality.

The shootings "awaken us to the reality of the time bomb that has stopped ticking — it has exploded," The Sowetan newspaper said in an editorial. "Africans are pitted against each other ... fighting for a bigger slice of the mineral wealth of the country. In the end the war claims the very poor African — again."

Police ministry spokesman Zweli Mnisi on Friday said an investigation into the shooting in Rustenburg is underway.

Marikana, South Africa

Political parties and labour unions, including the ANC, called for an independent inquiry. President Jacob Zuma is coming home from a regional summit in neighbouring Mozambique to address the crisis.

Makhosi Mbongane, a 32-year-old winch operator, said mine managers should have come to the workers rather than send police. He vowed that he was not going back to work and would not allow anyone else to do so either.

"They can beat us, kill us and kick and trample on us with their feet, do whatever they want to do, we aren't going to go back to work," he told The Associated Press. "If they employ other people they won't be able to work either, we will stay here and kill them."

On a chilly, sunlit Friday morning, police investigators and forensic experts combed the scene of the shooting, watched by about 100 people. A woman with a baby on her back said she was looking for her miner husband who had not come home Thursday night.

Police service defends officers

The South Africa Police Service defended officers' actions, saying in a statement that they were "viciously attacked by the group, using a variety of weapons, including firearms. The police, in order to protect their own lives and in self-defence, were forced to engage the group with force."

Shocked South Africans watched replay after replay of video of the shooting that erupted Thursday afternoon after police failed to get the striking miners to hand over machetes, clubs and home-made spears. Two police officers had been beaten to death earlier in the week.

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A miner holds up a machete as he sits with other workers during a strike calling for increased wages at the Lonmin platinum mine in Rustenburg on Thursday. (Stringer/AFP/GettyImages)

Some miners did leave, though others carrying weapons began war chants and marched toward the township near the mine, said Molaole Montsho, a journalist with the South African Press Association who was at the scene. The police opened up with a water cannon first, then used stun grenades and tear gas to try and break up the crowd, Montsho said.

Suddenly, a group of miners rushed through the underbrush and tear gas at a line of police officers. Officers immediately opened fire, with miners falling to the ground. Dozens of shots were fired by police armed with automatic rifles and pistols.

Images broadcast by private e.tv station carried the sound of a barrage of automatic gunfire that ended with police officers shouting: "Cease fire!" By that time, bodies were lying in the dust, some pouring blood. Another image showed some miners, their eyes wide, looking in the distance at heavily armed police officers in riot gear.

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Policemen keep watch on the protesters outside a South African mine in Rustenburg. (Siphiwe Sibeko/Reuters)

Poor South Africans protest daily across the country for basic services like running water, housing and better health and education — all of which were promised when racist white rule ended with the first democratic elections in 1994. Protests often turn violent, with people charging that ANC leaders have joined the white minority that continues to enrich itself while life becomes ever harder for the black majority.

Police often are accused of using undue force. Still, Thursday's shooting appalled the country, recalling images of white police firing at anti-apartheid protesters in the 1960s, 1970s and 1980s, though in this case it was mostly black police firing at black mine workers.

It remains unclear what sparked the miners' fatal charge at police. Mnisi, the police ministry spokesman, claimed the miners shot at police as well, using one of the weapons they stole from two policemen whom they beat to death on Monday.

"We had a situation where people who were armed to the teeth, attack and killed others — even police officers," the spokesman said in a statement Thursday night. "What should police do in such situations when clearly what they are face with are armed and hardcore criminals who murder police?"

President 'shocked and dismayed'

President Zuma said he was "shocked and dismayed at this senseless violence."

"We believe there is enough space in our democratic order for any dispute to be resolved through dialogue without any breaches of the law or violence," Zuma said in a statement.

Lonmin PLC chairman Roger Phillimore issued a statement Friday saying the deaths were deeply regretted. But he emphasized the mine considers it "clearly a public order rather than a labour relations associated matter."

The strike began last Friday. While it intially focused on wages, the ensuing violence has been fuelled by the struggles between the dominant National Union of Mineworkers and the upstart and more radical Association of Mineworkers and Construction Union. Disputes between the two unions escalated into violence earlier this year at another mine.

Clashes involving the two rival unions have claimed the lives of 10 people, including two police officers who were beaten to death by strikers. Two mine security guards died of burns suffered after strikers set their vehicle ablaze.

Mining drives the economy of South Africa, which remains one of the world's dominant producers of platinum, gold and chromium. Lonmin is the world's third largest platinum producer and its mine at Marikana produces 96 per cent of all its platinum. The violence has shaken the precious metals market, as platinum futures ended up $39, or 2.8 per cent, at $1,435.20 an ounce in trading Thursday on the New York Mercantile Exchange.

Lonmin stock plunged 6.76 per cent Thursday on the London Stock Exchange. The company's stock value has dropped more than 12 per cent since the start of the unrest.