The level of hunger worldwide has dropped in recent years but 26 countries still face extremely dangerous food shortages and are threatened by rising prices, a major report said on Tuesday. The Global Hunger Index, released by the Washington-based International Food Policy Research Institute (IFPRI), measures food insecurity. Its level has dropped by 26 percent since 1990, the institute said. But this still leaves several populations, mainly in South Asia and Africa, facing the threat of starvation, and the report -- endorsed by several major international aid agencies -- describes the situation as "serious". The four countries most at risk of hunger are Chad, Burundi, Eritrea and the Democratic Republic of Congo, the report concludes. Twenty-six countries, of the 122 evaluated, present a situation described as "alarming". Nevertheless, between 1990 and 2011, 18 countries escaped immediate danger, including Angola, Bangladesh, Ethiopia, Mozambique, Nicaragua, Vietnam and Niger. North Korea, the Comoros, Swaziland and Ivory Coast have got worse. The report was based on data gathered before the latest famine to strike the Horn of Africa and the authors warn the situation may have worsened. No data was available for Papua New Guinea nor war-ravaged Iraq, Somalia and Afghanistan, where the level of hunger cannot be measured. "The poorest and most vulnerable people bear the heaviest burden when food prices spike or swing unpredictably," said Klaus von Grebmer, lead author of the report and IFPRI communications director. "This report calls for action on several fronts to build resilience and mitigate the effects of volatility, particularly in countries where hunger is most severe," he said. "Growing demand for biofuels, extreme weather and climate change, and increased financial activity through commodity futures markets are the main causes of high and volatile food prices," the report concludes. It warns of "historically low levels of grain reserves, export markets for staple commodities that are highly concentrated in a few countries and a lack of timely, accurate information on food production." The report's authors urged politicians and policy-makers to curb wild price swings through market regulation and to cut back biofuel production, allowing more plants to be turned into food. "They also need to invest in climate change adaptation and mitigation and safeguard smallholder farmers against extreme weather-related shocks," said Maximo Torero, co-author of the report.