* Plotted aimed to kill Zuma and other top govt figures
* Involved mortar bomb and ground assault on ANC meeting
* Attack timed to coincide with 'Blood River' anniversary
BLOEMFONTEIN, South Africa, Dec 18 (Reuters) - Four white South Africans were charged with treason on Tuesday for plotting to bomb a conference of the ruling African National Congress (ANC) and kill President Jacob Zuma "execution style".
Prosecutor Shaun Abrahams said the men had planned to attack an ANC meeting, currently under way in the city of Bloemfontein, as a step towards carving an independent Boer republic out of Nelson Mandela's post-apartheid "Rainbow Nation".
The four, named as Mark Trollip, John Martin Keevy, Johan Prinsloo and Hein Boonzaaier, were brought into court surrounded by police and security guards armed with assault rifles.
Their lawyers did not enter a plea, and the men, aged between 40 and 50 and dressed in shirts and jeans, remained silent and impassive throughout the 20-minute hearing.
The vast majority of whites accepted the ANC victory in the 1994 election that brought Mandela to power and ended decades of white-minority rule. However, a tiny minority continues to oppose the historic political settlement.
The attack plan, which the plotters code-named "The Slaughter of Mangaung" - 'cheetah' in the local Sesotho language - included a mortar bomb attack on marquees housing ANC delegates.
That was to be followed by a ground 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," Abrahams said.
The plan was about a year in the making, he added, and was timed to coincide with the Dec. 16 anniversary of the 1838 Battle of Blood River, in which fewer than 500 Afrikaners defeated more than 10,000 Zulus.
The battle, in which 3,000 Zulus are said to have died against three wounded Afrikaners, has been mythologised in the history of the Afrikaners, the white minority descended from South Africa's earliest Dutch-speaking settlers.
The Afrikaner-dominated apartheid government commemorated Blood River as a public holiday, but since 1994, Dec. 16 has been rebranded "Reconciliation Day" in a bid to heal the wounds of three centuries of white dominance and conflict.
The four men were detained on Sunday and Abrahams said more arrests were likely to follow.
ANC spokesman Keith Khoza said the suspected plot amounted to "an act of terrorism that South Africa can ill afford".