Johannesburg - Three mine workers were killed in South Africa's restive platinum belt, a union said Monday, as efforts intensified to break a strike that is now in its fourth month.

The National Union of Mineworkers members were killed while on their way to work, or attacked at their homes, NUM spokesman Livhuwani Mammburu said.

Police said one was hacked to death, a second one was burnt to ashes in his house, while a third was found strangled to death along with his wife in their shack.

Six others were stabbed while walking to work, but survived.

The attacks appeared to bear the hallmarks of inter-union violence, but police could not confirm the motive.

Around 80,000 members of the Association of Mineworkers and Construction Union downed tools on January 23 demanding higher pay, dramatically cutting production in the world's largest platinum producing region.

Non-striking workers, including members of the National Union of Mineworkers have reported intimidation and violence by the striking majority.

“We know those who are on strike are behind the attacks,” NUM general secretary Frans Baleni told AFP.

“Our members are between a rock and a hard place.”

The most recent attacks come as platinum companies step up their efforts to break the strike.

Lonmin, the world's number three platinum producer said it was expecting a huge turnout of workers at the shafts this week after by-passing AMCU leadership and directly appealing to hard-up workers to return.

With many having to borrow from friends, family, or predatory lenders to make ends meet, Lonmin's call is likely to raise tensions.

“These people were planning the violent reaction. We know that yesterday they marched to the bus companies threatening to burn any buses that would transport workers,” said Baleni.

AMCU bosses have rejected a basic salary package of 12,500 rand by July 2017, saying they want that figure to take effect immediately. - Sapa-AFP