Four countries in Africa have "extremely alarming" hunger, said the report by the International Food Policy Research Institute (IFPRI), Concern Worldwide, and Welthungerhilfe.

The Democratic Republic of Congo (DRC) fared the worst in the hunger index, which is based on data from 2003-2008.

Three-quarters of the population in the vast central African country were under-nourished, and DRC also has one of the highest child mortality rates in the world, the researchers who compiled the index found.

Three factors were used to calculate the Global Hunger Index (GHI) - the proportion of undernourished people in a country, the prevalence of underweight children, and the child mortality rate.

"Protracted civil conflict since the late 1990s led to an economic collapse, massive displacements of people, and a chronic state of food insecurity," in DRC, the report said.

"Food availability and access deteriorated as food production levels dropped, and remote areas became even more isolated as a consequence of very poor infrastructure," it said.

The index ranks countries on a 100-point scale, with zero being the best score -- no hunger -- and 100 being the worst, although neither of these extremes is reached in practice.

A score higher than 20 indicates "alarming" levels of hunger and above 30, "extremely alarming" hunger.

Underweight children

DRC was one of four countries with "extremely alarming" hunger levels and the only country in this year's index with a score above 40.

The other three countries with very high hunger levels were Burundi, Eritrea and Chad. All have been involved in simmering or open conflict for many years.

With the exception of Haiti and Yemen, all 25 countries with "alarming" levels of hunger were in sub-Saharan Africa or Asia.

They were, in order of increasing hunger severity: Nepal, Tanzania, Cambodia, Sudan, Zimbabwe, Burkina Faso, Togo, Guinea-Bissau, Rwanda, Djibouti, Mozambique, India, Bangladesh, Liberia, Zambia, Timor-Leste, Niger, Angola, Yemen, the Central African Republic, Madagascar, the Comoros, Haiti, Sierra Leone and Ethiopia.

Along with Burundi, DRC and Eritrea, the Comoros - a coup-prone archipelago off the east coast of Africa - and Haiti had high proportions of undernourished people - more than 50% of the population.

Bangladesh, India, Timor-Leste and Yemen had the highest prevalence of underweight children under five - more than 40% in all four countries.

Afghanistan, Angola, Chad and Somalia had the highest child mortality rate, with 20% or more of each country's children dying before they reached the age of five.

North Korea was one of nine countries in which the hunger index went up - from 16.2 points in 1990 to 19.4 points in 2010.

The other eight were all in sub-Saharan Africa and include in all but three - Gambia, Swaziland and Zimbabwe - conflict was the cause.