The tense wait for the unveiling of the next leader of South Africa's ruling African National Congress (ANC) began after voting ended Tuesday in a tight contest between incumbent President Thabo Mbeki and ANC deputy leader Jacob Zuma.

Zuma was expected to quash Mbeki's controversial bid for a third five-year term at the party helm after taking the majority of nominations at the third level.

"So far so good," Mbeki would only comment after casting his ballot when asked his thoughts on how an unusually tumultuous leadership conference unfolded. Results of the vote were expected later Tuesday.

Voters queued from dawn outside the polling station at the University of Limpopo outside the northern town of Polokwane, where around 4,000 members have been gathered since Sunday to elect a new leader and discuss policy.

The mood was sober as delegates stood in line but outside the voting area senior party members close to Mbeki had to run a gauntlet of heckling Zuma supporters.

"Give a guy a chance," Defence Minister and ANC National Chairman Mosiuoa Lekota implored after being booed by members of the party's youth wing in scenes that have become staple fare at an ANC conference remarkable for the rebelliousness of delegates.

Phikelakhe Ntanzi from KwaZulu-Natal, who was dressed in full Zulu regalia including a leopard-skin hat and skirt for the vote, told Deutsche Presse-Agentur dpa. "It is the time for Zuma now."

Asked whether he support Zuma as an ethnic Zulu candidate, he said: "The ANC is not racist. That is not important for us."

Given the ANC's overwhelming electoral support - the party has over two-thirds of seats in parliament - the race between the centrist Mbeki and Zuma, who is the choice of the Left, was compared by many to a general election.

"In essence we have a one party system," a voter from Mpumalanga said.

"We are the major party on the African continent. We have to show democracy," another voter said. "Democracy must start from within the party."

This is the first time ANC members have been called on to elect a party leader since 1949. The leader is usually elected by party elders and their choice presented as a fait accompli to members. ANC membership grew to 621,237 in 2007.

Tuesday's vote comes at the end of a bruising campaign, which saw senior government members loyal to Mbeki booed by delegates Sunday in scenes uncharacteristic of the normally disciplined party.

For the past three days pro-Zuma and pro-Mbeki supporters have squared off in songs praising their candidate.

If elected, Zuma, is well placed to become South Africa's third president since democracy in 1994 at elections in 2009.

Mbeki's controversial bid for a third term as party leader, although he cannot seek a third term as president in 2009, has split the former liberation movement into Mbeki and Zuma factions.

Zuma, who was sacked by Mbeki as deputy president in 2005 on suspicion of corruption, has become a magnet for ANC members disillusioned with the party's top-down leadership style.

He still faces charges of corruption for allegedly taking backhanders from companies involved in a state arms deal.