New York - UN Secretary General Antonio Guterres said on Thursday that donors responded quickly to his warning in February that about 20 million people were at severe risk of famine in South Sudan, Somalia, Yemen and northeast Nigeria, but while "famine has been kept at bay" the need for humanitarian aid is increasing."The numbers of people at risk have grown," he told the Security Council, and "hunger continues for millions of people".Guterres appealed in February for $4.4bn to prevent famine and catastrophic hunger. He said that donors came forward with nearly 70% of the funds, which has helped provide food, health care and other support for nearly 13 million people every month."But while we have succeeded in keeping famine at bay, we have not kept suffering at bay," Guterres said. "In fact, in the past nine months, the need for humanitarian aid has increased in these four areas."Guterres told the UN's most powerful body that humanitarian aid is saving lives "but we have not dealt with the one major root cause of these food crises: conflict".He said about 60% of the 815 million people suffering from hunger "live in the shadow of conflict".Nigeria In northeast Nigeria, where Boko Haram extremists regularly carry out attacks, some 8.5 million people now need humanitarian aid, he said. The UN believes up to 700 000 people in parts of Borno and Yobe states "are completely inaccessible and may need urgent support".SomaliaIn Somalia, where large parts of the country's central and southern regions are still under the control or influence of al-Shabaab extremists, "more than 6 million people depend on humanitarian aid for their survival", he said. But al-Shabaab and other armed groups are targeting humanitarian workers and confiscating or destroying food and other aid.South SudanIn South Sudan, where the economy's collapse has led to widespread violence and increased criminality, Guterres said, the number of people who are "severely food insecure" - essentially getting one meal a day if they can - has increased from 5 million to 6 million since the beginning of the year. He accused government and opposition groups of blocking aid to areas where needs are urgent.YemenIn Yemen, the secretary general said "many millions are still suffering", despite assistance from the World Food Programme.Guterres said the parties to conflicts in all four countries have stated their commitment to international human rights and humanitarian law "but most of them have not followed through".He called on all parties and others to take urgent measures to address impunity.ExtremistsSpeaking to the Security Council, US Ambassador Nikki Haley also called humanitarian needs in the four countries "unprecedented", saying people without food, water and economic opportunities "are more likely to turn to extremist groups"."The plagues seem to come one right after the other," she said. "But they're not the wrath of God; they are the acts of men. In too many cases, they are the acts of leaders more interested in power or personal gain than the safety and security of their very own people."Haley said the main reason for the risk of famine in Yemen, South Sudan, northeast Nigeria, and Somalia "is that fighters are not letting food get to those who need it".She said additional funds are needed, but the council should go further "to hold those preventing access accountable for their crimes".