The United Nations warned on Monday that a regime assault against the opposition-held northwestern province of Idlib would lead to the century’s “worst humanitarian catastrophe.” It added that more than 30,000 people have been displaced this month alone as the regime prepares for its imminent offensive. Idlib province and adjacent rural areas form the largest piece of territory still held by Syrias beleaguered opposition. The regime has now set his sights on Idlib, and its forces have stepped up bombardment of the densely populated province since the beginning of the month. That has prompted an estimated 30,452 people to be displaced within Idlib and parts of adjacent Hama province between September 1 and 9, the UNs humanitarian coordination agency (OCHA) said Monday. "Were deeply concerned about this recent escalation of violence, which has resulted in the displacement of over 30,000 in the area. Thats something were monitoring very closely," OCHA spokesman David Swanson told AFP. Many made a dash for Syrias northern border with Turkey, with just under half seeking refuge in displacement camps and others living with local families or renting apartments. An AFP correspondent in Idlib has seen dozens of displaced families head towards the frontier in recent days to escape bombing elsewhere. On Monday, on the main highway running across the province, men on motorbikes headed north with their children on foot, herding dozens of sheep. Abu Jassim said he and his family were fleeing the latest bombardment near the southern town of Khan Sheikhun, after already having been displaced several times within the province due to the war. "They hit with four rockets so we escaped with our flock", he said. "We go wherever its safe," said the man in his 30s. "I have 30 sheep. Every day, I need water, hay and bran to feed them." The UN has said as many as 800,000 people could be displaced by a regime assault on Idlib and surrounding areas. Some three million people live in the zone now, about half of them already displaced by the brutal seven-year war and others heavily dependent on humanitarian aid to survive. Christy Delafield of Mercy Corps, one of the largest organizations delivering aid in Syria, said it has been hard for aid workers and communities to keep up with the displacement. “There is a lack of water storage capacity in many of the areas in which we operate, with just two or three days worth of water available to civilians,” she told Reuters. “The crossing points along the front lines between the government and opposition-controlled areas have been closed, and as a result, food prices have dramatically increased.” Syrias conflict has killed more than 350,000 people and forced millions more out of their homes, but the UN has warned a full-blown attack on Idlib could bring unprecedented suffering. On Monday, its humanitarian chief made an urgent appeal. "There needs to be ways of dealing with this problem that dont turn the next few months in Idlib into the worst humanitarian catastrophe with the biggest loss of life in the 21st century," Mark Lowcock told reporters in Geneva. He acknowledged that there were many factions and extremists in the province, but stressed that "there are 100 civilians, most of them women and children, for every fighter in Idlib". The conflicts three powerbrokers -- regime allies Russia and Iran and opposition backer Turkey -- agreed at a summit last week to "stabilize" Idlib, but few details emerged on how they would do. Delegations from the three countries will be in Geneva on Tuesday to meet the UNs Syria envoy Staffan de Mistura.