We shot in self-defence - SA police

South Africa's national police chief says her forces opened fire in self-defence after coming under attack by armed mine workers, leaving 34 people dead and 78 injured.

"The militant group stormed toward the police, firing shots and wielding dangerous weapons," Riah Phiyega told a news conference on Friday.

"Police retreated systematically and were forced to utilise maximum force to defend themselves. The total death (toll) of the protesters currently stands at 34, with more than 78 injured."

So far 259 people have been arrested on various charges stemming from the clash on Thursday at the platinum mine run by London-listed Lonmin, she said.

Police played video footage of their efforts to disperse striking miners, including a series of negotiations and crowd-control tactics such as firing teargas, water cannons, stun grenades and rubber bullets.

In one video, an officer begs the miners to disperse, saying: "We are not here to arrest you, our only problem is with the weapons."

Phiyega said police initially tried to break up the crowd into smaller groups to make them easier to disarm, but the miners refused to heed calls to disperse and lay down their weapons.

She insisted this justified the use of force.

"The police started by using minimum force, which is allowed in terms of our policy and the law," she said.

"Only when that did that not stop protesters, we then brought another support," she said. "And therefore I feel strongly and we feel ... that it was justified. We didn't want anyone to die."

General Sehlahle Masemola, a crime intelligence official, said police at the scene believed they wouldn't survive if they kept firing rubber bullets.

"For the police to protect themselves and for the police to protect their own colleagues, they realised that the usage of the rubber bullet is not ... applicable and to survive, they escalated the usage of force."

Miners who escaped with their lives see it differently.

"Our president Jacob Zuma, even now is not here. We have seven days now of strike, our president is not here," one says.

However South Africa's president Jacob Zuma says there'll be an inquiry into the shootings.

He says South Africa remains a vibrant nation, which continues to make progress.

"Today is not an occasion for blame, finger pointing, or incrimination. Today challenges us to restore calm."

Meanwhile the killings have sparked what will be the first New Zealand protest at a South African government institution in 20 years.

Organisers say New Zealanders didnâ t fight apartheid to pave the way for a small number of black millionaires to be created, at the expense of the majority.

Spokesman John Minto says a letter will be delivered to the South African consulate in Auckland this afternoon.

"It'll be a way in a sense New Zealand can express its, I guess revulsion at what's happened. New Zealanders have had a very strong, long, proud history of fighting against apartheid in South Africa and people are appalled."

Mr Minto says race-based apartheid has been replaced with economic apartheid.

Photo: A still from a video of the shooting of miners by police officers (YouTube)