Mine management stopped operations to ensure the safety of its employees and company property after some workers embarked on an unprotected strike earlier in the week, spokesperson Marion Brower said in a statement.
"This decision has been taken amidst rising tension at the mine, owing to incidents of intimidation, assault and threats of violence towards non-striking employees and damage to property on 15 January 2015."
About 5 000 members of the National Union of Mineworkers (NUM) downed tools on Tuesday night demanding the removal of chief executive Paul Dunne over what they say are unfair hiring and firing practices.
Strikers missed a deadline on Friday to return to work after workers resolved to defy a court order, saying they were "not compromising", branch chairperson Joseph Moloko told Reuters.NUM spokesperson Livhuwani Mammburu told Reuters that the strikers, who want the chief executive removed over what they say are unfair hiring and firing practices, had indicated they would "fight to the bitter end".
Northam said in a statement that there had been incidents of property damage, intimidation, assaults and threats of violence towards workers who were not striking.
NUM said it did not condone such behaviour and would have a news briefing at 15:30 about the strike.
"We don't encourage our members to embark on violence or damage property. We are totally against that," NUM spokesperson Livhuwani Mammburu said.
The company earlier warned that striking workers have a day to return to work. According to spokesperson Memory Johnstone, 40% of the 4 600 employees reported for morning shift on Thursday.
READ: Platinum strikers have day to return to work
An earlier Sapa report quoted Johnstone as saying: "Management has provided those remaining striking employees with a final opportunity to return to work by January 16 [Friday], failing which disciplinary measures will be instituted as provided for in the Labour Court’s interdict declaring the strike to be unprotected".
The Labour Court granted an interim interdict to end the unprotected strike on Wednesday.
NUM does not have the same reputation for violence and intimidation as its arch rival, the Association of Mineworkers and Construction Union (Amcu), which has poached tens of thousands of its members over the past three years in a brutal turf war on the platinum belt that has claimed scores of lives.
If the company's allegations about assaults and intimidation are true, it may indicate that NUM's rank and file is becoming more militant - a scenario that will send a chill through mining boardrooms.
The Zondereinde operation produces between 900 and 1 000 ounces of platinum daily, about 65% of Northam's output. The company said workers forfeit R2.4m of wages per day as the strike rumbles on.
The wider platinum industry is still recovering from a sometimes violent five-month strike last year by Amcu that hit Anglo American Platinum [JSE:AMS], Impala Platinum [JSE:IMP] and Lonmin [JSE:LON], the world's top producers of the precious metal.
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