Ballot counting in South Africa's fourth democratic election was to be completed by midday on Friday, but the African National Congress (ANC) has already feted a landslide win propelling party leader Jacob Zuma into the Presidency.

The only major question mark still hanging over the poll is whether the ruling party will retain its two-thirds majority and thereby the power to change the Constitution.

Zuma told supporters watching a fireworks display at ANC headquarters in Johannesburg on Thursday evening that he could "smell 70%", but with some 11-million votes counted, the party was in fact hovering near 66.6%.

The Democratic Alliance (DA) was clearly set to emerge from the election stronger, with its vote share on Thursday staying consistent at 16% plus - 4% up from the 2004 election.

The fledgling Congress of the People (Cope) was lying close to 8%, but from the moment ballot counting began it was patently never going to threaten the DA's status as the official opposition.

DA leader Helen Zille looked set to become Premier of the Western Cape and could even hope to claim to an outright majority in the province.

Her party was leading the ANC with more than 48% of the provincial vote. Results in key districts, including Mitchells Plain and the Gugulethu township, were still outstanding and could make for a suspenseful finish.

In all other provinces, the ANC was expected to sweep to victory. It won 69% of the vote in the Eastern Cape, while Cope established itself as the official opposition in the province and seemed on its way to do the same in Limpopo, the Northern Cape and the Northern Province.

The Independent Electoral Commission said it would only announce official results and the voter turnout at the weekend.