JOHANNESBURG: South African telecoms giant MTN on Wednesday denied an allegation that it had illegally repatriated $13.92 billion from Nigeria, saying the claim was without merit.

Lawmakers in the upper house of Nigeria's parliament agreed on Tuesday to investigate the allegation that MTN, Africa's biggest telecoms company, illegally transferred the money out of the West African country.

"The allegations made against MTN are completely unfounded and without any merit," MTN Nigeria chief executive Ferdi Moolman said in brief statement.

The allegation threatens to raise tensions between Nigeria and MTN just three months after the South African firm agreed to pay a reduced fine of 330 billion naira in a settlement with Abuja over unregistered SIM cards.

MTN is the largest mobile phone operator in Nigeria, which accounts for around one third of the company's revenues. The company had threatened to pull out of Nigeria during the dispute over unregistered SIM cards.

"It's not a good development but it may stem from the forex crunch in Nigeria. They don't want forex to leave the country unnecessarily," said Cobus de Hart, an analyst at NKC African Economics.

"It highlights the fact that the Nigerian central bank wants to maintain a firm grip on the forex market and this will obviously not bode well for investor sentiment," he said.

MTN shares fell more than 3 percent on Tuesday but opened 1 percent firmer on Wednesday.