South African workers of world No. 3 platinum producer Lonmin launched a wildcat strike on Tuesday, halting all of the company's mine operations and reigniting fears of deadly unrest that rocked the industry last year.

The platinum belt towns of Rustenburg and Marikana, which saw a bloody Lonmin strike last year, are a volatile flashpoint of labor strife and tensions are running high with job cuts and wage talks looming.

The share price of Lonmin slid over 6 percent and the rand currency hit 3-week lows, underscoring investor jitters over a potential repeat of the 2012 mines turmoil, which hammered platinum and gold production and triggered credit downgrades for Africa's largest economy.

Lonmin's Marikana mine was the epicenter of last year's strikes, where 34 protesting workers were killed by police in a single day in August. The bloodshed sparked widespread criticism of the African National Congress (ANC) government's handling of the mine troubles.

"All 13 shafts are not operational. Employees arrived at work but did not proceed underground," said Lonmin spokeswoman Sue Vey.

She said there was no indication at this stage as to why employees were on strike.

But a spokesman for the National Union of Mineworkers (NUM) said the strike appeared to stem from anger over the weekend killing of a local organizer from rival union Association of Mineworkers and Construction Union (AMCU).

A police statement at the weekend said that a 46-year-old man who was "alleged to be the regional organizer of AMCU" had been killed in a Rustenburg tavern on Saturday when an assailant shot him four times with a 9mm pistol.

AMCU has poached tens of thousands of disgruntled workers from the dominant NUM and the union turf war shows little sign of letting up.

Gideon du Plessis, deputy general secretary of the Solidarity trade union which represents skilled workers, said he understood AMCU was demanding the NUM close its office at Lonmin. AMCU now represents over 70 percent of the company's workforce.

Police said they were monitoring the situation but there were no plans at this stage to increase their presence. That would change should the protest escalate and spread beyond Lonmin's immediate properties.

"We are just doing our normal patrols," said Thulani Ngubane, police spokesman for the Northwest province, where Lonmin's operations are based. "At this point there is no march, there is nothing on the streets of Marikana."

Social tensions in the area have been stoked by plans by Anglo American Platinum , the world's top producer of the precious metal, to slash 6,000 jobs in a bid to restore profits. That is less than half the 14,000 initially targeted but unions have still vowed to fight against the lay-offs.

(Additional reporting by Sherilee Lakmidas and Agnieszka Flak; Editing by Pascal Fletcher)