Out of the blue, power shedding. Not a hint of a looming problem and then bang, the lights go out.

Power cuts rippled across South Africa on Thursday, blacking out parts of major cities and spurring warnings from state utility Eskom that unexpected shortages could extend into next week.

The cuts, which Eskom attributed to power-station maintenance and the shutdown of one unit at the country's only nuclear power plant, caused power failures stretching from Cape Town to Johannesburg.

South Africa's power woes have raised political temperatures in the past, with critics accusing the government of failing to address the energy crunch plaguing Africa's biggest economy as it gears up to host the Soccer World Cup in 2010.

Minister of Public Enterprises Alec Erwin was "confident that South Africa as a whole will not be plunged into darkness", said a statement from his office.

Eskom spokesperson Fani Zulu said the company would try to ensure that a 2 000MW shortage would not take a heavy toll on homes and appealed to the public to switch off non-essential electrical equipment.

"The situation is critical. We expect about two hours of shortages a day. We will tap reserve resources. Hopefully we will resolve the problem early next week," he said.

One unit was shut down in the Koeberg plant outside Cape Town -- Africa's only nuclear power station -- which has been beset by blackouts. Zulu said 900MW of the facility's 1 800 had been cut. It supplies 50 % of the electricity in the Western Cape, South Africa's tourist hub.

Eskom's managing director for transmission, Jacob Maroga, said earlier in a statement carried on the Sapa news agency that the shortage would amount to 4 600MW out of a total national capacity of about 36 000.
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