Aerial bombings in Sudan\'s Blue Nile state have forced nearly 2,000 people to flee to neighbouring Ethiopia, the UN refugee agency has said. Most of the refugees were women, children and elderly people, with some walking for three weeks, it said. The Sudanese army has denied previous accusations that it has conducted bombing raids in Blue Nile state. Since September its troops have been battling rebels allied to South Sudan, which became independent in July. About 28,700 people have fled the area since fighting erupted last month. The UNHCR said the new arrivals reported air strikes in areas between Blue Nile\'s capital, Damazin, and the town of Kurmuk, near the Ethiopian border. \"They tell us they fled bombings and fear of bombings by Antonov planes,\" the UNHCR said in a statement. \"There are also reports that armed militia on the Sudanese side of the Kurmuk border have warned the community to leave the area, possibly in preparation for a ground offensive,\" it said. Ethiopian troops The Sudanese army denies bombing Blue Nile, but says its troops are advancing on Kurmuk after last week capturing the town of Sali, 29km (18 miles) away. The rebels, however, deny losing control of Sali. Map Last month, the Sudanese government declared a state of emergency in Blue Nile and appointed a military governor for the region. It also lodged a complaint in September with the UN Security Council, accusing South Sudan of sending 25 armed land cruisers to support rebels in Blue Nile. South Sudan denied the allegation. Blue Nile is one of three border areas - along with South Kordofan and Abyei - where fighting has broken out since South Sudan\'s independence. Many rebels in the three regions fought alongside southerners during the decades-long civil war that ended with Khartoum agreeing to the south\'s independence. The rebels accuse Sudan\'s army of now launching a campaign of \"ethnic cleansing\" in the three regions, while Khartoum accuses them of trying to ignite a new civil war. In July, the UN Security Council sanctioned the deployment of 300 Ethiopian troops to monitor a demilitarized buffer zone between the two countries. Last month, the defence ministers of Sudan and South Sudan - Abdelrahim Mohamed Hussein and John Kong Nyuon respectively - signed an agreement to ease tension at border crossings. They agreed that teams with six soldiers from each side and six Ethiopian peacekeepers would be stationed at the crossings to investigate any reports of violations.