The heavily armed police and supported by armored vehicles were being set up roadblocks son of barbed wire when they were overwhelmed by some 3,000 employees at the mine, located 100 km northeast of Johannesburg and operated by the company Lonmin.
Police fired bursts of automatic weapons on a'' group of miners who surged from behind a vehicle.
At least ten attackers were killed, showing footage shot by Reuters Television. A journalist from the South African agency Sapa said he counted 18 bodies. A spokesman for the Democratic Alliance, the main opposition party in South Africa, said meanwhile that the toll could rise to 38 dead.
Police refused to confirm the casualties.
"Police officers, to protect their own lives, were forced to use force with the group," she said in a statement. "This led to fatal injuries in many people."
Negotiations for several days by police with the main miners union, the Association of Juvenile and construction (AMCU), had previously failed, prompting authorities to order the evacuation of strikers and deploy for this purpose near of 3,000 police.
Marikana strikers have not made any explicit claims even if the conflict is largely due to the rivalry between the AMCU National Union of Mineworkers (NUM), whose rule lasted for two decades.
"Scene of apartheid"
Clashes between rival unions had already been dead for ten Marikana a week, including two policemen.
The South African President Jacob Zuma said on Thursday was "shocked and dismayed" about what appears to be one of the bloodiest police operations since the end of the apartheid regime of apartheid in 1994.
"I asked the agencies responsible for law enforcement to do their utmost to regain control of the situation and that the perpetrators are punished," he said in a statement.
The Ministry of Police for his part said that the officers had done so after having first tried to disperse the crowd peacefully.
"The Minister considers that, given the volatile situation, the police did their best," said SMS spokesman of the police, Zweli Mnisi.
Representatives of the AMCU accused the police of killing.
Some commentators have compared the scene of the drama to the darkest episodes in the history of apartheid, when police opened fire on demonstrators in black neighborhoods.