Abuja, Rabi'II 25, 1436, February 14, 2015, SPA -- Boko Haram militants have launched an attack on Gombe, a major city in north-eastern Nigeria, prompting local officials to impose a 24-hour curfew on residents. Hundreds of militants attempted to penetrate the city centre and were confronted by ground troops who retaliated with air support, according to a resident. "There was heavy exchange of fire between the terrorists and our soldiers, especially around the military barracks," Mustapha Ibrahim told dpa. "The sound of gunfire is everywhere." Nigeria has postponed a general election that was set to take place on Saturday amid concerns about the insurgency raging in the north of the country. More than 157,000 people have fled the violence in north-eastern Nigeria and have crossed the borders to Niger, Cameroon and Chad. Nearly 1 million people have been displaced within Nigeria. -- SPA 18:23 LOCAL TIME 15:23 GMT www.spa.gov.sa/w