BLOEMFONTEIN, South Africa — Four white South Africans were charged with treason on Tuesday over a suspected plot to bomb a conference of the ruling African National Congress (ANC) and execute President Jacob 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 the central city of Bloemfontein surrounded by security guards armed with assault rifles.

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 now under way in the city.

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

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.

However, a tiny handful continues to oppose the historic settlement in Africa's biggest economy.