South Africa's state run power utility Eskom has suspended the managers of two power stations it blames for exacerbating breakdowns leading to widespread power outages, it said on Friday.

Eskom generates the majority of South Africa's power, but for years has struggled to manage supply from ageing coal-fired power plants and has imposed intermittent blackouts.

After about four months of steady supply it imposed power outages in July for about a week.

Blackouts returned in August, worsening on Wednesday this week as the firm ramped up cuts from "stage 2" to "stage 4", which requires up to 4,000 megawatts (MW) to be shed from the grid. On Thursday it downgraded the outages to "stage 3".

Eskom blamed breakdowns at its power stations.In a statement it said it had suspended the managers of the Tutuka and Kendal power stations pending disciplinary inquiries.

Further interventions are ongoing at the Kriel and Duvha power stations, the firm said.

"Whilst it is true that the ageing fleet is plagued by legacy issues of neglect and omitted maintenance and is therefore susceptible to unpredictable breakdowns, it is also true that the situation is exacerbated by serious issues of apathetic behaviour by some management staff," said Eskom.

Eskom said there was 5,000 MW of capacity currently on planned maintenance and 10,950 MW, about 12 units, lost to unplanned breakdowns. This has resulted in an energy demand deficit of about 3,000 MW, aggravated by higher demand during this week's cold front.