UN relief coordinator John Holmes pleaded for increased aid from donors Tuesday to avert a humanitarian catastrophe in Africa's drought-hit Sahel region. The outgoing head of the UN Office for the Coordination of Humanitarian Affairs (OCHA) said more than 229 million dollars was still needed to respond to the crisis in Niger, the worst hit of the countries in the region. Donors have so far either committed or delivered more than 142 million dollars. Some 7.1 million people, roughly 47 percent of the Niger's population, is facing food insecurity, Holmes said, citing an April survey. Malnutrition has also significantly increased, with a June survey showing a global acute malnutrition prevalence exceeding 15 percent, up from 12.3 percent last year. Over 300,000 children under the age of five are said to be at risk of acute malnutrition in Niger, including 20 percent who will suffer medical complications, OCHA said. In neighboring Chad, Holmes said donors had so far only pledged 45 percent of the 542 million dollars requested and that 1.6 million people face food insecurity and malnutrition. Another 600,000 people in Mali and 300,000 in Mauritania are similarly at risk. UN officials point out that last year's poor rains have resulted in a 30 percent decline in cereal output in Niger compared with 2008, while production of food for livestock is 62 percent below requirements. Food prices also remain high, despite a decline from a peak in 2008. Holmes, a Briton who is to step down late next month as UN humanitarian chief, underscored the need for an urgent and coordinated response from the international community to tackle the emergency. He said that UN agencies and non-governmental organizations were present on the ground in Niger and better prepared to respond than during a similar crisis five years ago. 'What we need to do is step up that capacity even further and make sure it is resourced because people have no food or where there's food, they need money to buy it,' added Holmes, who visited Niger in April. 