The battle between the Syrian regime and opposition factions for the northwestern Idlib province could leave 1 million children at risk, warned the United Nations children’s agency on Friday. Many of the children already live in refugee camps and the food, water, and medicine are already in short supply in the largely rural province, which is now home to over 1 million Syrians displaced from their homes by regime offensives in other parts of the country, said UNICEF. The agency said a battle for Idlib, the last major bastion for Syrias political and military opposition, would exacerbate an already dire humanitarian situation there and potentially displace 350,000 children. The warning came as regime forces bombed towns and villages at the edge of the contested area, killing at least three civilians, among them one child, a local search-and-rescue group said. The Civil Defense, also known as the White Helmets, said regime aircraft bombed homes in the towns of Khan Sheikhoun, Altmana, Sukayk and Alteh. Hussein Kayal, a media activist in Khan Sheikhoun, said the attack was sudden and shattered nearly three months of calm in the town, as the regime focused on defeating opposition forces in south Syria. "Its been three hours of non-stop bombing," he said. Regime forces bombed opposition-held towns in adjacent Hama province as well, the Britain-based Syrian Observatory for Human Rights reported. The Observatory said the regime was moving ground forces to the north in preparation for an all-out assault, including tanks and artillery. The UN has warned the consequences of such a campaign could be catastrophic. "War cannot be allowed to go to Idlib," said Jan Egeland, a top UN humanitarian adviser on Syria. There are 2.9 million people living in Idlib and surrounding opposition-held areas, according to UN estimates. The UN has appealed on Turkey to open its border to refugees, should the regime decide to attack the province, Egeland said. Turkey, which has established itself as a sponsor of the opposition in northern Syria, already hosts some 3.5 million Syrian refugees — the most of any nation. It has also established 12 monitoring posts in Idlib and deployed 1,000 troops in the province. But Kayal in Khan Sheikhoun said there were doubts the Turkish presence would deter the Syrian regime from attacking. "People here wont be surprised if theres a ground attack. The Turkish points are weak - they wont repel anything. Were scared that if anything happens, (the Turkish forces) will pull out immediately," he said. Syrias war has killed at least 400,000 people, according to monitors. More than 11 million — or half of Syrias pre-war population — have been displaced from their homes, according to the UN, including some 5.6 million who have been made refugees abroad.