CAPE TOWN: South Africa's President Jacob Zuma on Sunday called for calm over the killing of white supremacist leader Eugene Terre'Blanche, as police arrested two of his farm workers.

The 69-year-old Afrikaans Resistance Movement (AWB) leader was found with facial and head injuries, a machete on his body and a knob-headed stick nearby on his farm in the north-west after an alleged dispute with the workers.

Police arrested two men, aged 21 and 15, with a police spokeswoman telling local media the pair had said they had argued with Terre'Blanche over not having been paid for work done on his farm.

Zuma urged South Africans to remain calm as opposition parties and groups warned that the far-right leader's killing had created a potentially explosive situation.

"The President appeals for calm following this terrible deed and asks South Africans not to allow agent provocateurs to take advantage of this situation by inciting or fueling racial hatred," said a statement from Zuma's office.

"No one is allowed to take the law into his own hands," said the statement, the SAPA news agency reported.

"It is against this background that the murder of Terre'Blanche must be condemned, irrespective of how his killers think they may have been justified. They had no right to take his life."

Terre'Blanche's supporters, who wear khaki uniforms and the organisation's swastika-like symbol, violently opposed South Africa's all-race democracy and campaigned for a self-governing white state.

Their campaign included bomb attacks ahead of the 1994 polls, which ended the white minority apartheid state.

Violence on farms, which remain overwhelmingly in white hands 16 years after apartheid ended, is high in South Africa with 1,248 farmers and farm workers killed between 1997 and 2007.

The main opposition Democratic Alliance said the murder happened in a region where "racial tension in the rural farming community is increasingly being fuelled by irresponsible racist utterances", SAPA reported.

Terre'Blanche's murder came amid heightened race tensions over a song with the refrain "kill the boers" (Afrikaans for farmers), which has been adopted by the ruling African National Congress' (ANC) fiery youth leader Julius Malema.

Two South African courts have banned the use of the song, which outraged opposition parties and interest groups, who argued it incites violence against whites.

Zuma's ANC has said it will challenge the bans, arguing that the song was part of the legacy of South Africa's liberation struggle.

Afriforum, one of the groups that successfully challenged the "kill the boer" song in court on Thursday, also appealed for calm.

"It is urgent for all to remain calm under circumstances which are very tense and potentially may be destructive," it said in a statement.

And the minority party Freedom Front Plus, led by South Africa's deputy agriculture minister, said people should not react emotionally to the AWB leader's slaying.

It also called on leaders to speak out against the "kill the boers" slogan.

"The murder of Eugene Terre'Blanche creates an explosive situation and is condemned in the strongest possible terms," SAPA quoted party spokesman Pieter Groenewald as saying.

A one-time police officer, Terre'Blanche was released from prison in 2004 after serving time for having tried to kill a black security guard.

He was well known as a powerful speaker, was well as for his piercing blue stare and grey beard.

Terre'Blanche fought for a white homeland for the Boers after forming the AWB in 1973 with six others to oppose what they believed were moves towards majority rule by the white apartheid nationalist government.