Nigeria, Jan 09 (ANI): Boko Haram militants have killed hundreds of people and burned down homes in the northeast Nigerian town of Baga in the past two days, in a second killing spree since seizing control there at the weekend, witnesses said. Two locals said the Islamist insurgents began shooting indiscriminately and burning buildings on Tuesday evening in raids on the civilian population that carried on into Wednesday. It is seen as the gravest threat to Nigeria, Africa's biggest economy, and a headache for President Goodluck Jonathan ahead of an election on February 14. Soldiers fled Baga over the weekend when the Sunni jihadist group overran a nearby army base. The district head of Baga, Abba Hassan said that at least 100 people were killed when the group first took over the town on the edge of Lake Chad. Abubakar Gulama, who escaped without his family to Monguno, 40 km (25 miles) away, said he crossed "many dead bodies on the ground" and that "the whole town was on fire". Meanwhile, United Nations Chief Ban Ki-Moon issued a personal appeal for the release of children kidnapped by extremist groups.