The United Nations on Wednesday sought $500 million more in aid funding for 2011 as serious drought hit the Horn of Africa, bringing the total sum needed for 31 countries to $7.9 billion for the year. \"The most worrying development is the drought in the Horn of Africa,\" said the UN in its mid-year review of its 2011 humanitarian appeal. \"Major parts of several countries are already at crisis stage of food availability, nutrition, and livestock survival,\" it added.