South Africa's electricity company Eskom said on Friday unplanned breakdowns at its plants were affecting just under 12 000 megawatt of generating capacity, forcing it to burn diesel and use water from pumped storage schemes to augment its base load.

"Load-shedding will be required all day to cater for further trips and to create capacity to replenish water reserves for our pumped storage schemes," said the State-owned utility, which supplies about 95 percent of the country's power needs, mostly from coal.

"Breakdowns are at 11 996 MW as at 06:30 this morning. We continue to use diesel for our open cycle gas turbines and water at pumped storage schemes to supplement capacity."

Eskom said it was trying to reduce the level of unplanned breakdowns to below 9 500 megawatts to minimise load-shedding and avoid having to implement rotational blackouts next week.

"Eskom will provide a prognosis for the long weekend later today," it added.

The power utility says it is working with police to investigate alleged sabotage at its Tutuka power station in Mpumalanga province which wiped 2 000  megawatt off the grid and prompted it to implement Stage 6 load-shedding on Monday, which entails suppressing up to 6 000 MW of demand to avoid a total collapse of the grid.

On Friday it was implementing Stage 2 load-shedding until 11 pm.