Over 30,000 people in South Sudan's war zone regions face death by starvation, the United Nations said Thursday, warning that tens of thousands more are on the brink of famine. While an official famine has not been declared, the report describes the worst conditions yet seen in a 22-month civil war marked by atrocities and accusations of war crimes, including the blockading of food supplies. "At least 30,000 people are living in extreme conditions and are facing starvation and death," the U.N.'s Food and Agriculture Organization, the U.N. children's agency UNICEF and the World Food Program said in a joint statement. Those worst affected are in the northern battleground state of Unity, once the country's key oil producing region, but now scene of some of the heaviest fighting, including the mass abduction and rape of women and children. Famine is a technical measure, assessed by the Integrated Food Security Phase Classification, which classifies hunger on a scale of one to five. The IPC, whose members include FAO and WFP, said famine had not been officially declared as it was hard to get data from conflict zones. "There is a great concern that famine may exist in the coming months but it may not be possible to validate it at that time due to lack of evidence as the result of limited access to the affected areas and populations." South Sudan's government Agriculture Minister Beda Machar told a news conference there was no "famine" in the country and the food situation has in fact improved. "We advise against the irresponsible use of a word such as "famine" by stakeholders, including the media." While large parts of South Sudan's Unity and Upper Nile regions were already classified as being just one step short of famine, termed "Emergency" or "phase 4," areas in Unity have been declared to be in "phase 5" for the first time, with 860,000 people in those extreme conditions. Level 5 is classified as "Catastrophic Food Insecurity," and when stretched to 20 percent of the population, becomes famine. While poor rains have impacted harvests in some areas, the worst conditions are in war zone areas, with the extreme conditions sparked by conflict not climate. Intense fighting in some parts of the country has forced humanitarian groups to pull out, and they say displaced families are surviving on just one meal a day. In extreme cases, people fleeing violence survive by eating water lilies. "People are on the edge of a catastrophe that can be prevented," WFP chief Joyce Luma said. Both sides of the conflict are accused of having perpetrated ethnic massacres, recruited and killed children and carried out widespread rape, torture and forced displacement of populations to "cleanse" areas of their opponents. "Since fighting broke out nearly two years ago, children have been plagued by conflict, disease, fear and hunger," UNICEF chief in South Sudan Jonathan Veitch said. "Their families have been extraordinary in trying to sustain them, but have now exhausted all coping mechanisms. Agencies can support, but only if we have unrestricted access. If we do not, many children may die." Tens of thousands of civilians have been killed from fighting and the country's economy has been destroyed, with soaring inflation causing sharp spikes in food prices. A year ago famine was averted only after a huge intervention by aid agencies. Aid agencies including Oxfam warned Thursday of "appalling conditions" and "unbearable suffering" in Unity state, while World Vision said there were "alarmingly low harvests" elsewhere in the country.