Northam Platinum workers say will not return to work due to safety concerns

* South Africa platinum sector has been marred by labour violence

* NUM says six members have been murdered at Northam

* Company urges workers to resume after output suspended Monday

* Sector is struggling with depressed prices, rising costs (Adds AMCU comment, Northam urges workers to resume)

By Ed Stoddard

JOHANNESBURG, June 7 (Reuters) - Workers at Northam Platinum's South African mine said on Tuesday they would not return to work until management and police provided them with safety guarantees after a spate of murders, despite appeals from the company that it was safe.

Northam suspended production at Zondereinde mine on Monday after a worker was fatally stabbed during a clash between members of the National Union of Mineworkers (NUM) and the rival Association of Mineworkers and Construction Union (AMCU). The company on Tuesday urged workers to return to the mine.

The clashes heightened concern over a potential repeat of outbreaks of union violence that resulted in deaths and operational stoppages across the sector.

South Africa is the world's top producer of the precious metal used for catalytic converters in automobiles, but the industry is battling with labour unrest, soaring costs and depressed prices.

AMCU president Joseph Mathunjwa told Reuters members of his union will not return to work as they still felt unsafe.

Mathunjwa said Northam had sent text messages to its members asking them to resume work but they would not heed the call.

"How are workers going to go back when they are being attacked and stabbed?," he said.

NUM has said that one of its members was the victim of a fatal shooting on Sunday and that five other workers have been murdered at Northam.

A spokeswoman for the company said that five employees have died over the past year in what she described as separate isolated incidents that occurred off the mine site and were being investigated by the police.

The Zondereinde mine produces about 300,000 ounces of platinum a year, according to Northam's website, and accounts for about 70 percent of the company's revenue.

Northam, the world's third largest platinum miner by market value, reported a first-half loss in February partly due to low platinum prices and impairments.

NUM spokesman Livhuwani Mammburu said the union, which is the majority union at Northam, planned to hold a mass meeting at the mine later on Tuesday and wanted the police and management to address the workers and assure them about the steps being taken to quell the violence.

A wildcat strike at Lonmin (LSE: LMI.L - news) 's Marikana mine in 2012 erupted in similar circumstances and ended with the police shooting 34 miners dead.

The AMCU has unseated NUM as the main union in the platinum belt in recent years in often-violent circumstances.

"This is not about union rivalry to us, it is about our members being killed," Mammburu said of the situation at Northam.

The latest flare-up also comes ahead of what are expected to be tough wage talks at Anglo American Platinum, Impala Platinum and Lonmin. (Additional reporting by Zandi Shabalala; Editing by James Macharia and David Evans)