South Africa’s government expressed its concern over the $5.2 billion fine imposed by Nigerian authorities on MTN, but said the row would not affect relations between the countries.

Nigeria, MTN’s biggest market, stepped up its efforts to ensure all telecoms operators verify their subscribers amid terrorism concerns, and set an August deadline for companies to comply with the laws.

MTN’s failure to cut off users with unregistered SIM cards from its network led to the fine, which it has since been trying to reduce after holding talks with the authorities. Nigerian Communications Commission (NCC) said MTN had failed to disconnect 5.1 million subscribers between August and September.

Reuters reports South African cabinet minister Jeff Radebe said the dispute is between MTN and the Nigerian authorities, before adding that the country’s government is “obviously concerned about this matter”.

He also said the country’s two presidents had not discussed the matter.

Meanwhile, Tony Ojobo, a spokesman for the NCC, told the Associated Press the regulator won’t buckle under pressure from MTN, stating that Nigeria’s four service providers had agreed to a $1000 fine for each unregulated SIM in 2011, with MTN the only company not to comply.

“MTN should operate in the law – the same rule of law that protects investment,” said Ojobo.

MTN spokesperson Chris Maroleng said the company is still in talks with authorities at all levels “to try and arrive at a speedy resolution”.

NCC earlier this week also extended MTN’s operating licence in the country to 2021, which Maroleng said is an indication that the country still wants MTN to operate there.