JOHANNESBURG, South Africa (CNN) -- Rising tensions at a South African platinum mine exploded Thursday in grisly violence as police fired on striking miners.

Blood-stained bodies lay strewn about a field in a police response reminiscent of the days of apartheid.

Police have not released a death toll, but a South African Press Association reporter counted 18 corpses. It's feared more could be dead.

The striking miners were believed to be armed with guns, machetes and sticks, CNN affiliate E-TV reported.

Police fired tear gas and then used a water cannon to disperse the strikers congregating atop a hill. The mine workers retaliated by firing at police, and a storm of gunfire lasted about three minutes, E-TV said.

The situation remained tense Thursday night after what was the deadliest day in almost a week of violence at Lonmin's Markinana mines. The violence was sparked by a rivalry between unions that wield a lot of power and influence in South Africa.

A statement from Lonmin said 10 people had died before Thursday's incident -- eight mine workers and two policemen, who were reported to have been hacked to death.

Roger Phillimore, the chairman of Lonmin, said his company regretted the loss of life "in what is clearly a public order rather than labor relations associated matter."

"We are treating the developments around police operations this afternoon with the utmost seriousness," he said.



Production at the world's third-largest platinum producer came to a halt as workers, mostly rock drillers, embarked on a wildcat wage strike last Friday over a wage dispute. The miners are demanding substantial salary increases.

The company had issued an ultimatum to the striking workers: Return to work by Friday or face dismissal. That was before Thursday's bloodshed.

"The violence that has occurred cannot be condoned and has no place in the way that labor relations and inter-union relations should be conducted," said Mildred Oliphant, the minister of labor. "The loss of life has been particularly tragic and unnecessary."

Earlier this year, at least three people were killed during a six-week strike at the world's second-largest platinum mine, Impala Platinum.

That violence also was blamed on union rivalry, though the two implicated unions, accused of trying to outdo each other in negotiating wages, deny instigating the clashes.

Frans Baleni, head of the dominant National Union for Mineworkers, said Monday that members were under siege.

"Our members have been attacked, and that cannot be said to be clashes or rivalry, it is pure criminality," he said.

The newer Association of Mineworkers and Construction Union also denied any blame.

CNN's Nkepele Mabuse contributed to this report.