The strike, in which employees are demanding a basic salary of R12500, entered its fourth day yesterday. The miners have vowed not to go back to work until their demand has been met.

They also vowed to picket outside the mine's main entrances "as long as management does not involve police", according to regional officials of the National Union of Mineworkers.

Management has warned that the strike is "illegal and unprotected" and gave the miners ultimatums on Wednesday and yesterday to return to work. On both occasions, workers stuck to their decision to return only after their demand had been met.

According to parent company Petra Diamonds' group support manager Egbert Klapwijk, the demands were outside their current two-year wage agreement which was reached at the collective bargaining chamber.

Klapwijk said the agreement only ends on June 30 2013.