By Devon Maylie and Alexis Flynn

MARIKANA, South Africa--Around 2,000 protesting workers at Lonmin PLC (LMI.LN) Wednesday marched to the site of a recent clash with police in which 34 people were killed, as miners reiterated demands for their monthly salaries to be tripled.

The clash and strike at Lonmin last month brought workers' grievances to the fore at other platinum and gold mines raising companies' concerns about their operations.

Wednesday, police watched on as the protesters, some carrying sticks, proceeded to the Marikana mine singing songs and chanting slogans such as "down with sellout, down with NUM" (the traditional union) and "our people are dying, Zuma is killing us."

Men wearing the green shirts of the Association of Mineworkers and Construction Union led the group and spoke to the management. The mine manager, Jan Thirion, guarded by security guards, came and out called on the protesters to wait for negotiations to end.

But the protesting group said they will be back Thursday to make sure those breaking the strike haven't returned. Lonmin's output has been stopped since Aug 10 at Marikana and in the past week less than 10% of staff have turned up.

"This is about the money...we don't care if we die. We won't return until Lonmin gives us 12,500 rand, ($1,488)" said Vincent Tyobeni, one of the ringleaders of the march Wednesday.

Meanwhile South Africa's second largest gold producer, Gold Fields Ltd. (GFI), said a week-old strike at its KDC east mine was due to end on the night shift Wednesday. But trouble resurfaced at Impala Platinum Holdings Ltd. (IMP.JO) which said it had received new wage demands emanating from a strike in February that again threatened to destabilize its largest mine.

The resumption in tensions came as South Africa's Trade and Industry Minister Rob Davies sought to reassure foreign investors in a series of meetings in London Wednesday.

Speaking to an audience that included Goldman Sachs' doyen of emerging economies, Jim O'Neill, and Ann Grant, Standard Chartered Bank's Vice Chairman for Africa, Mr. Davies described the events at Marikana as "a tragedy" that wouldn't be allowed to happen again.

Mr. Davies avoided mention of Marikana or the ongoing labour unrest for much of his speech, concentrating for the most part on detailing theoretical ways that South Africa could leverage its relations with China, India and Brazil, as well describing its position as a gateway for investors to access growth markets on the rest of the African continent.

While the labor unrest had negatively impacted the shares of companies like Lonmin, it hadn't affected foreign investment, Mr. Davies said.

"We have not seen an impact on foreign direct investment. The impact has largely been felt in the shares of the companies concerned," said Mr. Davies.

In response to the four-week-long strike Lonmin has said it will have to start to consider shaft closures soon because it can't stay open without production. But first it's trying to resolve the standoff in talks that resumed Wednesday between unions and the company.

However, analysts highlight that a solution is not that simple.

"Now this is about union-on-union action and dissatisfaction with larger, social issues wrapped into wage issues and strikes. It's much harder for FDI (foreign direct investment) investors to get a handle on. You see Lonmin has been powerless to resolve this at all, given it's not really just about wages," said Peter Attard Montalto, emerging market economist at Nomura International.

At the heart of the strike is frustration over living conditions and pay, but it's also playing out in a battle between emerging AMCU and governing ANC-ally National Union of Mineworkers, as they fight for membership.

(Jenny Gross in London contributed to this article)

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

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