At the trades on the Johannesburg Stock Exchange, MTN shares fell 21.4% to 84.35 rand, after they touched 83 rand, which was noted in 2009.
The central bank of Nigeria said that the funds were illegally exported abroad, because the bankers of the company could not verify that MTN had fulfilled all the currency rules.
MTN refutes the allegations.
Demand from the central bank of Nigeria is the latest setback for MTN in Nigeria, the most profitable group in South Africa, but increasingly and its most troubled market.
This happens two years after MTN, the largest telecommunications company in Africa, has agreed to pay more than $ 1 billion to put an end to the dispute in Nigeria over unregistered SIM cards.
This case underscores the risks of the MTN strategy for working in emerging markets, which made it one of South Africa's largest commercial achievements in the history of apartheid with more than 20 countries.
This money is more than half the market capitalization of MTN, and analysts say that demand risked further undermining Nigeria's efforts to get rid of the image as a risky market for international investors.
The essence of the statement is that MTN used improper certificates to convert loans of shareholders in its Nigerian unit to preferred shares in 2007.
Nigeria said that due to the conversion, the dividends paid by MTN Nigeria to the parent company between 2007 and 2015 – $ 8.1 billion – were illegal and must be returned.
MTN said in a statement: "No dividends have been announced or paid for by MTN Nigeria, except in accordance with the certificates of capital import issued by our bankers and with the approval of the CBN (Central Bank of Nigeria) in accordance with the requirements of the law."
"I wonder why this did not attract the attention of MTN many years ago.
"You simply can not do business in an environment where such things will happen," said Greg Davies from the investment house Cratos Capital in Johannesburg.
The Central Bank of Nigeria also fined four banks, including the Standard Bank unit in Nigeria, Stanbic IBTC, for their role in moving money from Africa's largest economy.
On Wednesday, the central bank said that he fined Stanbic IBTC for $ 1.8 billion ($ 6 million) for violating the rules of foreign exchange operations and ordered him to return 2.6 billion dollars, which he repatriated on behalf of clients, including MTN.
Standard Bank, the statement said, his unit "is not the beneficiary of any remittances made on behalf of customers, and denies any imputations of atrocities."