Africa's largest mobile operator, MTN, has been ordered by Nigeria's communication authority to bar subscribers who had not yet linked their SIM cards to their identity numbers.
Subscribers who have not submitted their identity numbers are to be barred by 28 February, and those who have submitted, but not verified, are to be barred by 29 March.
Nigeria is MTN's biggest market, accounting for more than 40% of its revenue, with almost 78 million subscribers.