“The process is underway and we are writing letters informing them that no money will be allowed to leave South Africa,” foreign ministry spokesman Clayson Monyela, said without offering further details.
Local daily Business Day said the money is invested through the $5 billion Libya Arab Africa Investment Co (Laaico), through Libya Oil Holdings, Libya African Investment Portfolio and Libyan Foreign Investment Company (Lafico).
In South Africa, it owns Ensemble Hotel holdings, including the luxury Michelangelo Hotel in Johannesburg.
Libya holds billions of dollars in assets in Africa through subsidiaries of its $70 billion sovereign wealth fund.
The South African presidency said on Wednesday that Gaddafi called Zuma “to explain his side of the story”.
The statement said: “South Africa has openly condemned the loss of life and attacks on civilians and reported violations of human rights in Libya.”