At least 99 percent of the 20.6-million South Africans who registered as voters are expected to turnout to make their crosses on polling day, the Independent Electoral Commission said on Monday -- provided it did not rain.

IEC chairwoman Brigalia Bam added that many rural South Africans had to go to great trouble and travel long distances to be able to register to vote.

"It is very rare that when you have gone through all that, and we give you a public holiday, you will decide not to go and vote," she said.

"People are bound to turn up. We are just praying, and I do every morning, that it doesn't rain."

Some 93,000 people with special needs such as the disabled and pregnant women started casting their votes on Monday, while South Africans travelling overseas had already voted on April 7.

Bam was not concerned about political clashes in the hotly-contested province KwaZulu-Natal, which she said were isolated and were being contained effectively by the police.

She said political campaigning had been generally peaceful and conducive to the holding of free and fair elections, with political parties displaying maturity and observing the IEC's code of conduct.

"I wish to thank all political parties, especially their representatives, for showing leadership."

All political campaigning has to come to an end by Tuesday.

Bam said some 204 observer missions would monitor the poll, mainly from African countries.

These included groups from the African Union and the Southern African Development Community.

International organisations like the Commonwealth, European Union and United Nations had declined to send observer teams saying instead they were satisfied with the level of maturity of South Africa's electoral democracy, she said.

There were also 3,000 local election observers, 2,000 of them from KwaZulu-Natal alone.

"The spirit of voluntarism has so much gripped KwaZulu-Natal during these elections that many other applications of observers in that province had to be turned down.

On the security front, the commission was working with the police, national intelligence and defence force to ensure that the poll was trouble free.

Two police members would be based at every polling station.

"With Operation Decor in place, involving several thousand soldiers and police members, law and order will be maintained to the satisfaction of all stake holders, especially the voters," Bam said.

She stressed that people like journalists, and long distance taxi and bus drivers, who may find themselves in districts other than where they had registered to vote, would be allowed to cast their ballots elsewhere.

A total of 16,966 polling stations would open at 7am on Wednesday and close at 9pm - Sapa.