President Muhammadu Buhari has said that the failure of South African telecommunication giant, MTN  to disconnect millions of unregistered users aided the activities of Boko Haram.

“You know how the unregistered GSM are being used by terrorists… That was why  NCC (Nigerian Communications Commission) asked the MTN, Glo and the rest of them to register GSM,” Buhari told a joint a press conference held with the visiting President Jacob Zuma of South Africa.

He continued: “Unfortunately MTN was very slow and contributed to the casualties. And that was why the NCC looked at its regulations and imposed that fine on them.”

Nigerian Communication Commission  (NCC) had ordered all phone line operators to disconnect unregistered SIMs by mid-2015 on security grounds but MTN missed the deadline.

The company was consequently fined a $3.9 billion. It has since paid out $250 million towards the penalty.

The affair cast a shadow over the build-up to the visit of South African President Jacob Zuma and was expected to have been high on the agenda when he met Buhari for talks in the capital, Abuja.

Buhari emphasised that the country had no intention of witch-hunting MTN. He said the fine became imperative since unregistered lines were a security risk.

“The concern of the federal government was basically on the security, not the fine imposed on the MTN,” he said.

Zuma arrived in Abuja on Tuesday morning in a visit which observers see as an attempt to mend fences between Africa’s largest economic powers.

Pretoria is putting a positive spin on the visit, talking up the pair’s “good bilateral political, economic and social relations” and potential new business opportunities, AFP reports.

Zuma has a sizeable ministerial and business delegation in tow and announced after meeting Buhari that “over 30 bilateral agreements and memoranda of understanding” had been signed.

“These agreements cover a wide range of cooperation areas including trade and industry, transport, energy, defence and security and immigration among others,” he said in a speech.

He made no mention of MTN, which challenged the fine in court but withdrew its case to enable negotiations for an agreement.

Nigeria has asked South Africa for closer defence ties, including special forces training in operations against Boko Haram, military spokesman Rabe Abubakar announced late on Monday.

But the MTN affair — and complaints from other South African firms in Nigeria — have dominated discussions against a background of tensions.