* About 925 million hungry in 2010 vs 1.02 billion in 2009
* Improving economic conditions, lower food prices help
* WHO chief warns of food crisis after floods, drought
By Catherine Hornby
ROME, Sept 14 (Reuters) - The number of people in the world suffering chronic hunger has declined for the first time in 15 years, due to improving economic conditions and lower food prices, the United Nations' food agency said on Tuesday.
But the World Health Organisation warned flooding in Pakistan and Russia's drought threatened to spark a food crisis that could endanger the world's poorest people.
About 925 million people are undernourished in 2010, down from a record 1.02 billion last year, which was the highest number in four decades, the Food and Agriculture Organisation (FAO) said in a report.
Despite the decline in chronic malnourishment reported by the FAO, food riots in Mozambique this month, protests in Egypt, rising grain prices due to Russia's drought and climate change have pushed the issue of hunger and food security up the global agenda.
The FAO said most of the world's hungry people live in developing countries, where they account for 16 percent of the population in 2010.
While that marks an improvement from a level of 18 percent in 2009, the FAO warned it was lagging a U.N. target to halve the proportion of undernourished people in developing countries from 20 percent in 1990-92 to 10 percent in 2015.
"The fact that nearly a billion people remain hungry even after the recent food and financial crises have largely passed indicates a deeper structural problem," the FAO said.
"Governments should encourage increased investment in agriculture, expand safety nets and social assistance programmes, and enhance income-generating activities for the rural and urban poor."
World leaders are expected to declare at a United Nations summit next week that the set of goals aimed at drastically reducing poverty and hunger worldwide by 2015 are achievable, according to a draft document.
The number of hungry people in the world had been rising for more than a decade, reaching a record in 2009 triggered by the economic crisis and high domestic food prices in several developing countries.
The improvement in food security in 2010 was mainly a result of better access to food due to improving economic conditions, as well as lower food prices after two years of bumper cereal harvests, the FAO said.
It said while cereal production in 2010 was forecast to be lower, the overall supply situation was adequate.
But FAO Director-General Jacques Diouf added: "There are obvious reasons for concern as markets remain nervous and therefore vulnerable to any sudden shock."
Russia imposed a grain export ban last month after a drought ruined swathes of crops while Pakistan is still grappling with floods which have destroyed over 3.4 million hectares of crops.
"With both countries suffering the loss of crops ... we have to anticipate another global crisis of soaring food prices that will hit poor households the hardest," WHO Director General Margaret Chan said in a speech in Moscow.
Chan said the floods in Pakistan had shown the dangers climate change posed for the health of the world's population.
"Sceptics who doubt the reality of climate change would do well to look closely at recent events in China, Pakistan and here in the Russian Federation," she said.
"The downpours, mudslides, floods, heat waves, droughts, wildfires and ruined crops match closely the predictions of climate scientists. These scientists have repeatedly warned the world to expect an increase in the frequency and intensity of extreme weather events and this is what we are seeing."
(Additional reporting by Guy Faulconbridge in Moscow; Editing by Janet Lawrence)
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