CEO Sifiso Dabengwa said in The Star newspaper that MTN’s Irancell venture, in which the South African firm holds a 49 percent stake, added four million subscribers to its existing 34.6 million last year. Revenue was up 20 percent to 11 billion rands ($1.4 billion, one billion euros) in 2011.

He said MTN would only pull out if South Africa joined the US-led sanctions over Tehran’s disputed nuclear programme.

“We are guided by South African government policies internationally, in the same way US companies are prohibited from doing business in Iran. Unless the government says (otherwise), we will just have to manage,” he said.

“This is a challenge because outside institutions are prohbited from dealing with Iranian institutions,” he said.

“We have been able to repatriate funds. We’re working through other ways as opposed to working through official banking systems, obviously with all the checks and balances with our auditors,” he said.

MTN’s Iran operations came under the spotlight last month when rival Turkcell sued the company in a US court, claiming that the South African group had bribed government officials in exchange for rights to an Iranian GSM mobile operating licence.

South African petrochemical giant Sasol is reviewing its operations in Iran due to the sanctions risk.