Sifiso Dabengwa, chief executive, MTN, Africa's biggest mobile company has resigned over the $5.2 billion fine imposed on the company by Nigerian Communications Commission (NCC) for failing to deactivate 5.1-million unregistered SIM cards on its network.
MTN said on Monday that nonexecutive chairman Phuthuma Nhleko had agreed to act as executive chairman for a maximum period of six months while the company identified a successor for Mr Dabengwa.
Dabengwa, tendered his resignation with immediate effect, saying it was "in the interest of the company and its shareholders".
The fine, which amounts to double MTN's profit last year, was for failing to cut off unregistered mobile users.
The firm was given until 16 November, just two weeks, to pay the penalty.
The company is in talks to reduce the fine.
"Due to the most unfortunate prevailing circumstances occurring at MTN Nigeria, I, in the interest of the company and its shareholders, have tendered my resignation with immediate effect," said Mr Dabengwa in a statement.
He had been in the post since 2011.
It is thought that the Nigerian government imposed the fine after the kidnapping of a former finance minister, Chief Olu Falae. The kidnappers used an unregistered Sim card from MTN to demand a ransom.
Nigeria is MTN's biggest market, with 28.5 million subscribers, followed by Iran and South Africa.
