LAGOS, Nigeria–Nigeria’s biggest cellphone operator MTN has warned that its network faces shutdown due to fuel shortages that have crippled the nation. The company, the biggest subsidiary of the South Africa-based MTN Group, said it needed a ��significant quantity of diesel in the very near future to prevent a shutdown of services across Nigeria.�� Despite being Africa’s biggest oil producer, Nigeria lacks domestic refineries, forcing crude to be exported and products such as petrol and diesel to be imported. To keep costs to consumers low, the government sets prices below the market rate and pays the difference to importers. But the global slump in oil prices has hit Nigeria hard and oil marketers claim they have not been paid in full. Fuel depots have closed as a result pending payment of the arrears, with the situation worsened after oil and gas union workers walked out over the sale of two oil blocks. The crisis comes just days before President Goodluck Jonathan leaves office, handing over power to Muhammadu Buhari this Friday. Many petrol stations have now run out of fuel both for vehicles and generators, on which most people and businesses rely because of the woeful public electricity supply. On Friday, the Ministry of Power said electricity production was at an all-time low of 1,327 megawatts, according to local media reports. Diesel generators power most of MTN’s base stations and switches across the country but supplies were running low, said the company’s corporate services executive Akinwale Goodluck. The Lagos Chamber of Commerce and Industry earlier this week warned the crisis could force firms to lay off staff. The warning from MTN, which has more than 55 million subscribers, is a sign that businesses were now being hit.