South Africa's police ministry says at least 30 people were killed Thursday, when officers opened fire on striking workers at a platinum mine.

A ministry official said Friday that police opened fire with automatic weapons at the Lonmin PLC mine, about 120 kilometers northwest of Johannesburg.

Around 3,000 people have walked off the job in the past week over a pay dispute. Lonmin issued a statement earlier Thursday, warning workers they would be dismissed if they did not return to work by Friday. After the clashes, the management issued a statement saying some of the strikers were armed.

Prior to Thursday's deadly clash, 10 people, including two police officers had been killed in violence related to the mine strike.

Lonmin is the world's third largest platinum producer.