South Africa's national police chief said Friday that 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.

"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 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 begged 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 that justified the use of force.

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

"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."