The Federal Government has asked MTN Group to pay $2 billion tax being the telco’s computed tax liabilities for importation of foreign equipment and payments to foreign suppliers over the past 10 years.

According to a news report sourced from Reuters indicated that the notice of the tax bill was served barely a week after the Central Bank of Nigeria (CBN) ordered MTN’s Lagos-based unit to pay a fine of $8.1 billion over illegally repatriated funds abroad.

The telecommunication company in a statement hinted it had commenced talks with Nigeria’s Attorney General about an investigation into tax compliance, outlining the background to the case of the money sent out of the country.

The telco stated: “In this process, his (the Attorney General’s) office made a high-level calculation that MTN Nigeria should have paid approximately $2.0 billion in taxes relating to the importation of foreign equipment and payments to foreign suppliers over the last 10 years.”

MTN, whose Nigerian business brings in a third of its annual core profit, or Ebitda, stated that its total payment of around $700 million over the 10-year period fully settled the amount owing under the taxes in question.

The latest demand is also coming two years after MTN agreed to pay more than $1 billion to end a dispute with Nigeria over its failure to de-activate unregistered SIM cards.

Shares in MTN dropped 5.6% to R81.95 as of 12:50 GMT, bringing losses since last Thursday, when the central bank issued the $8.1 billion demand, to nearly 25%.

Commenting on the development, a portfolio manager at Vestact in Johannesburg, Byron Lotter, said that these are old issues that had been investigated and closed but now being re-opened.

“I’m not surprised that a lot of people are selling and saying ‘these guys are just too volatile, I’m out’. I wonder if MTN are thinking the same”, Lotter added

According to online reports, South African hotels and casino group, Sun International, is also reported to be finalizing plans to exit Nigeria following clashes with regulators and shareholders.

A retailer, Woolworths and food maker, Tiger Brands, had both exited Nigeria over the last three years.

MTN, which has expanded in more than 20 frontier markets that include war-ravaged Syria and Afghanistan, called the latest demands by Nigerian authorities “regrettable and disconcerting”.

It, however, assured that it would continue to engage with the relevant authorities on all these matters, adding that “we remain resolute that MTN Nigeria has not committed any offences and will vigorously defend its position.”

Nigeria’s attorney general, Abubakar Malami, declined to comment, referring Reuters to a spokeswoman at the ministry of justice. She could not immediately be reached by phone.

MTN’s regulatory troubles in the oil-rich country come ahead of next year’s presidential election, in which Nigerian President Muhammadu Buhari, who swept to power on promises of tougher regulations and a stronger fight against corruption in a 2015 election, is seeking re-election.