South Africa President Jacob Zuma has ordered an official inquiry into the shooting dead of 34 miners by police.

He described the events yesterday, in which 74 others were injured, as “shocking”.

"This is unacceptable in our country which is a country where everyone feels comfortable, a country with a democracy that everyone envies," Mr Zuma said in a statement read at a news conference.

After more than 12 hours of official silence, Police Minister Nathi Mthethwa confirmed said the death toll from the operation at the Marikana mine, 100km northwest of Johannesburg, was likely to rise.

Over 250 people were arrested during the violence.

Police opened fire with automatic weapons when 3,000 striking drill operators armed with machetes and sticks ignored orders to disperse.

"A lot of people were injured and the number keeps on going up," Mr Mthethwa said in an interview on Talk Radio 702.

He defended the police, saying officers had come under fire from the miners, members of the Association of Mineworkers and Construction Union.

"From amongst the crowd, people opened fire on police and the police retaliated," he said in earlier comments re-broadcast on the same station.

Police crime scene investigators searched the site of the shooting, collecting spent cartridges and bloodstained traditional weapons such as machetes and spears, which were carried by the miners.

They said firearms were also recovered at the scene.

London-headquartered Lonmin has been forced to shut down all its platinum operations, which account for 12% of global output.

Its shares have fallen more than 13% since inter-union rivalry at Marikana boiled over a week ago.

South Africa is home to 80% of the world's known platinum reserves, but rising power and labour costs and a steep decline in the price of the precious metal this year has left many mines struggling to stay afloat.

Prior to yesterday’s deaths, ten people, including two policemen, had died in nearly a week of fighting between AMCU and NUM factions at Marikana.

At least three people were killed in a similar round of fighting in January that led to a six-week closure of the world's largest platinum mine, run nearby by Impala Platinum.