The walkout in the Western Cape and KwaZulu-Natal provinces, home to two of the nation's three largest cities, was part of a drive by the Congress of South African Trade Unions (COSATU) and its allies to pressure the government to tilt policy to the left in Africa's biggest economy.

It will culminate in a national strike on August 6

The mass action came amid rising political tension in South Africa and fears of a downturn in its economy. Growth has averaged about 5 percent in recent years but dropped sharply in the first quarter of 2008.

Business leaders and foreign investors worry that labour unrest could combine with an electricity crisis and soaring world oil prices to produce a toxic cocktail for South Africa, which is a net importer of energy.

"The proposed rolling mass action will affect productivity and drive prices higher. We are looking at millions of rands, if not billions in lost productivity," said Neren Rau, chief executive of the South African Chamber of Commerce and Industry.

Unions, which were instrumental in helping to end white minority rule, accuse President Thabo Mbeki of pursuing pro-business policies that have favoured a wealthy elite at the expense of millions of workers and the poor.

A sharp increase in the price of petrol and basic staples, such as milk and bread, and a series of interest rate hikes have stoked labour's determination to thwart the policies.

Unions are also furious over job losses linked to the electricity crisis that began in January. The state-owned power utility Eskom has been rationing electricity to mines and other large industrial customers as well as residents.

Mines are among those affected by the rolling strikes that will include all of the country's nine provinces in the coming weeks. It is not clear how many miners will walk off the job.

"This protest is turning into a declaration of war against the rampant exploitation of the interests of the wealthy over the poor, while the government chooses the side of the wealthy," said Tony Ehrenreich, COSATU's regional secretary in the Western Cape.

"The Mbeki administration has overseen this crisis and has promoted it by their overly business-friendly policies ..."

SUPPORT FOR ZUMA

COSATU, which has more than 1 million members, and its allies in the small but influential South African Communist Party (SACP) have thrown their support behind Jacob Zuma, the new leader of the ruling African National Congress (ANC).

Zuma, whose left-leaning views have at times been considered populist, overwhelmingly defeated Mbeki for the party leadership late last year, and is the frontrunner to succeed the South African leader when he is forced to step down next year.

The ANC leader's presidential ambitions could be derailed by a corruption trial expected to begin later this year.

Although Zuma has tried to reassure investors that there will no major policy changes, his support for expanded subsidies for the poor and a greater state role in the economy has chilled the business community.

Mbeki and his powerful finance minister, Trevor Manuel, have so far resisted the left's attempts to loosen the tight fiscal policy that many analysts credit for the country's decade-long economic boom.

The South African Reserve Bank has also refused labour's demand to stop raising interest rates. The central bank has lifted its repo lending rate by 500 basis points in the past two years in a bid to tame inflation, which is around 11 percent.

COSATU and the SACP, which are in a formal alliance with the ANC, say the poor have been hurt most by the higher cost of borrowing.