"We are saddened and regret this further loss of life which has just happened, bringing roughly the total number of deaths to 30," said general secretary Frans Baleni.

"It is extremely regrettable. We hope a full investigation will be done and hope the perpetrators will be brought to book."

A shoot-out between police and strikers at the mine left at least 18 people dead or wounded.

The count was made by a Sapa reporter on the scene, who said the victims were lying in the veld.

The shooting erupted when police sought to disperse armed striking workers who had gathered on a hill in the area.

Ten people, including two security guards and two police officers, had already been killed in violent protests the past week.

The platinum producer issued a warning on Thursday for strikers to return to work within 24 hours or face dismissal.

"The striking rock drill operators remain armed and away from work. This is illegal under the Labour Relations Act," Lonmin said in a statement.

Lonmin said it lost 15,000 ounces of platinum production since the illegal strike started last Friday.