Nigeria’s communication regulator ordered mobile operators not to activate, sell or register new SIM cards until the completion of an assessment into whether providers have complied with data regulations.

In a statement, The Nigeria Communications Commission said the suspension would be for the duration of an audit of operators’ current bases and new registrations would only be allowed “where absolutely necessary” with permission from the government.

Failure to comply, the regulator added, would be met with “strict sanctions” including the possible withdrawal of operating licences.

Ensuring the identification of mobile users has been a priority of Nigerian authorities for several years, with SIM registration rules first put in place during 2011. MTN’s local unit received a massive fine for contravening rules in 2015.

In January, Nigeria imposed further regulations requiring users to complete digital identification procedures with government agency National Identity Management Commission and provide the details to their mobile network provider.

Nigeria has four major mobile operators, with GSMA Intelligence figures for Q3 estimating MTN as the largest with 75 million connections, followed by Glo Mobile (54 million), Airtel’s local operation (44 million) and 9Mobile (13 million).