South Africa's governing ANC has denied involvement in alleged business deals linked to the deaths of 13 soldiers.
The soldiers were killed in the Central African Republic (CAR) last month, when rebels seized the capital in a coup to depose President Francois Bozize.
Media reports say the South African troops were guarding the president in return for lucrative mining contracts.
The South African government says they were training government forces and providing security.
According to South African Defence Minister Nosiviwe Mapisa-Nqakula, nearly 300 troops were stationed in CAR and they found themselves outnumbered as rebels took the capital Bangui on the weekend of 23-24 March. As well as the 13 dead, another 27 of them were injured.
South Africa's Mail and Guardian newspaper reported on the alleged business interests in an article on Thursday, prompting the African National Congress to threaten the newspaper with legal action.
It accused the paper of urinating on the graves of "gallant fighters who put their lives on the line in service of our country and our continent".
"The ANC rejects with contempt the damaging and malicious claim by The Mail and Guardian that South African soldiers were sent to the Central African Republic to protect ANC business interests," it said.
It added that "the ANC as an organisation does not have business interests in CAR".
Meanwhile the opposition Democratic Alliance has said it will present a motion to parliament demanding the withdrawal of South African troops from CAR - although it is possible that no troops remain there.
Its leader Helen Zille said it looked as if the South Africans were in CAR to defend the regime.
The mission "was reportedly undertaken against expert military advice" and was "allegedly to protect the business interests of a politically connected elite, both in South Africa and the Central African Republic", she said.
"If this is so, President Zuma's position both as president of the republic and commander in chief of the armed forces, becomes untenable," Ms Zille added.