Scammers have used emails, phone conversations and social media to impersonate South Africa's President Cyril Ramaphosa in order to request for funds.
The president's office said on Wednesday that the scam messages had also portrayed Ramaphosa as having endorsed payments or contracts between third parties.
It did not reveal details on the scale of the scam but urged the public to terminate all future contact with the scammers.
Those who have already sent funds to the scammers have been told to contact the authorities.
"The president does not request any funds or endorse any payments or contracts between third parties, whether through websites, adverts, social media, emails, letters, texts or phone conversations," a statement from the presidency said.
It is unclear how long the scam has been running and the nature of the contracts involved.
Cybercrime and impersonation fraud have been on the rise in South Africa, according to local reports, with fears the country could become the cybercrime capital of Africa.
