South African President Jacob Zuma has been re-elected as the leader of the governing party, the African National Congress (ANC).

Zuma beat Kgalema Motlanthe, his challenger and the country's vice-president, as about 4,000 delegates cast their ballots on Tuesday at the ANC's conference in Bloemfontein.

Zuma will now be the party's presidential candidate and almost certain winner in the 2014 national elections.

Anti-apartheid era hero Cyril Ramaphosa has been elected as Zuma's deputy. Four other senior positions were also filled.

Motlanthe on Monday said he would not stand again to be deputy leader, but it is likely he will be offered a senior position by Zuma.

Al Jazeera's Haru Mutasa, reporting from Bloemfontein, said: "It is likely that Zuma will offer Motlanthe something in order for the party to remain united."

Zuma has been accused of corruption and failing to bridge the gap between South Africa's rich and poor.

'Boer' plot

Meanwhile, four white South Africans were charged with treason over a suspected plot to bomb the conference and execute Zuma and other top government officials.

The four, named as Mark Trollip, John Martin Keevy, Johan Hendrick Prinsloo and Hein Boonzaaier, were brought into court in Bloemfontein on Tuesday.

State prosecutor Shaun Abrahams said the men wanted to establish an independent Boer nation and that they were planning an assault on the ANC mass meeting. Boer, meaning farmer, denotes descendants of Dutch-speaking settlers in the country.

The plan included a mortar bomb attack on marquees housing ANC delegates, before an assault targeting Zuma and cabinet ministers as they had dinner, Abrahams told the court. Zuma and others were to be shot "in execution style", he said.

The intention of the group, which had been trying to buy AK-47 assault rifles, was "directly aimed at eliminating the leadership of this country", said Abrahams.

The vast majority of South Africa's whites accepted the ANC's victory in the 1994 election that brought Nelson Mandela to power and ended decades of white-minority rule.

A handful of whites, however, continue to oppose the historic settlement in Africa's biggest economy.

Source: Al Jazeera and agencies