The funds will enable Africa's largest wireless carrier to finance capital expenditure to increase the reach and efficiency of its network in Nigeria, Chief Financial Officer Adekunle Awobodu said by phone from Lagos.
MTN has also started the process of listing its shares on the Nigerian Stock Exchange.
The company had announced plans to raise as much as 400 billion naira last year, and later signed to a 200 billion naira credit line with a group of banks. MTN is "currently arranging" for another 200 billion naira, according to Awobodu.
It registered 20.35 billion ordinary shares with the country's Securities and Exchange Commission last week, with about 20 percent expected to be listed on the Lagos bourse this week.
MTN has 65.6 million subscribers in Nigeria, or 38 percent of the market, according to February data provided by the Nigerian Communications Commission.