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By Devon Maylie

MARIKANA, South Africa--Workers clamored for higher wages Wednesday at two more platinum companies in South Africa's mining heartland, less than a week after police shot and killed 34 people at a violent protest at Lonmin PLC's (LMI.LN) Marikana mine.

Miners at the world's biggest platinum producer Anglo-American Platinum Ltd. (AMS.JO), or Amplats, and Royal Bafokeng Platinum Ltd. (RBP.JO) echoed the Lonmin workers in calling for better pay and working conditions.

Amplats said a group of workers submitted demands including a wage increase at its Thembelenmi mine. The company said there was no strike yet.

On Tuesday night, Royal Bafokeng Platinum said about 500 rock drillers embarked on an illegal strike. They blocked the entrance to its North shaft, which accounts for 40% of its production, preventing other miners from showing up to work.

The wage protests and ongoing disruption to the Marikana mine's production briefly lifted platinum prices to their highest level in four months as investors took in the possibility of a production halt at Amplats, which accounts for 40% of global platinum supply. At 1737 GMT, spot platinum was trading 1.5% higher at $1,522.50 a troy ounce.

The new protests could also bring a spread of the violence that has led to 44 deaths at Lonmin in one week as a result of clashes between workers and police.

The Lonmin strike wasn't the first violent clash seen this year in the platinum industry. A group of rock drillers launched an illegal strike at Impala Platinum Holdings Ltd. (IMPUY) in February, shutting down its largest mine and causing the company to lose 120,000 ounces of platinum production. Police said three died in clashes between workers.

At the Marikana mine Wednesday, the striking Lonmin workers met with South African President Jacob Zuma near the site of last week's shootings. Mr. Zuma's visit was his first public appearance near the site of the shootings, though he had visited the mine hospital last Friday. His promises of mediation, however, failed to placate the workers.

Speaking to a crowd of several hundred miners who gathered in a grassy field 500 meters from where the shootings took place, Mr. Zuma attempted to show common cause with the strikers, refuting their claims that the government had authorized the shooting and was overlooking their concerns.

"I sympathize with all who fell victim," said Mr. Zuma.

The president, whose mother tongue is Zulu, addressed the workers in Xhosa. Many Lonmin employees come from the Eastern Cape, where the language is most widely spoken.

The audience, sitting next to homes made of tin or cement blocks, met Mr. Zuma's comments with heckles. One Lonmin worker, who identified himself as a local leader with the Association of Mineworkers and Construction Union, or AMCU, said the president wasn't listening to them and hadn't paid his respects to the site where protesters had died in violent clashes with police.

The problems at Lonmin began Aug. 10, when 3,000 rock drillers launched an illegal strike for higher wages.

The protests quickly led to violence. Fighting among workers at first claimed 10 lives, including two police officers. Then, police fired live ammunition into a crowd Thursday during a standoff with protesting employees, killing another 34 workers.

A rivalry between the established National Union of Mineworkers and the emerging AMCU added to the tension. Workers wearing new green T-shirts with the AMCU insignia patrolled the area Wednesday and said protesters weren't allowed to speak to the media.

A dozen workers wandered around the site wearing the AMCU shirts T-shirts and carrying sticks. They said they wouldn't speak about their grievances until after the dead are buried on Thursday.

Mr. Zuma, whose government has been criticized for its failure to intervene earlier, said he has been meeting with Lonmin's management and police to understand what happened and to find a way to prevent it from happening again. He said that he will be able to comment further on what transpired after a recently-mandated Commission of Inquiry completes its work.

"Workers have a right to express their grievances," Mr. Zuma said, adding that he will continue to meet with the company and community leaders. He said he had heard the workers' demand for a wage increase to 12,500 rand a month and would take it to the ministerial committee and the company.

The president's efforts at mediation, however, appeared to leave the strikers underwhelmed.

Lonmin employee Sekeni Nkumbi said he's staying away from the mine until the management agrees to meet workers over demands to increase wages.

"I am getting old and have very little to show for the years I have worked," said 54-year-old Mr. Nkumbi, who has worked at Lonmin for seven years.

Write to Devon Maylie at devon.maylie@dowjones.com

(Laura Clarke and Alex MacDonald in London contributed to this report.)