The owner of a South African mine where police killed 34 people last week says striking workers must return to the job Monday or face being fired.

Lonmin PLC said in a statement Sunday that the deadline is a “final ultimatum.”

About 3,000 people have joined the strike since August 10 to demand higher wages.

The protest turned violent last Thursday when police opened fire on striking workers. The national police chief says her forces shot in self-defense.

President Jacob Zuma has ordered a national week of mourning beginning Monday to remember the lives of all South Africans who died violently, especially the 44 people who have been killed in recent violence at the mine in Marikana township.

A committee appointed by the president is due in Marikana Monday to assist the victims' families. A separate team will lead an official inquiry into the shootings.

Mr. Zuma called on the nation to unite against violence and reaffirm a belief in peace, stability and order.

Lonmin is the world's third-largest platinum producer.

The company says it will pay education costs for the children of employees who died. It calls the strike “illegal” and says the action is “disappointing and damaging” to its labor relations.