Almost a billion people are going hungry and millions more could slip over the edge unless the world takes urgent action, aid agency Oxfam warns in a new report.

"This should be a wake-up call for all those who believe that the food crisis will be over soon," Oxfam's Chief Executive Barbara Stocking said.

Recent food price rises have helped swell the number of hungry to around 963 million - an increase of 109 million people in about two years, according to U.N. figures quoted in the report, A Billion Hungry People.

Oxfam warned that the global economic recession and climate change would likely exacerbate the problem.

"Leaders have a window of opportunity to prevent a worse situation resulting from the triple crunch of the economic crisis, climate change, and energy and water scarcity," Stocking said.

"Failure to act will see millions more people falling into hunger."

The British aid agency released the report on the opening day of a U.N. conference in Madrid on food security.

Although global food prices have fallen in the last few months, they are not back to previous levels, and are likely to rise sharply again in the future, Oxfam said.

Sub-Saharan Africa is a region causing particular concern, with the number of hungry people increasing by 43 million over the last 15 years to 212 million, according to the report.

Oxfam said much more must be done to address the underlying issues that cause the chronic hunger now affecting one in six people in the world.

The report includes recommendations for reforming the humanitarian aid system and calls on poor countries to invest more in agriculture.

Developing countries must increase protection measures for vulnerable populations - including employment creation schemes for those at risk of hunger, it says.

For their part, rich countries must ensure long-term predictable funding to developing countries for investment in agriculture and climate change adaptation.

Another report, published on Monday by British think tank Chatham House, says climate change, water scarcity and competition for land will make it hard to meet an expected 50 percent rise in demand for food by 2030. The Feeding of the Nine Billion - a reference to the world's ballooning population - also calls for more investment in agriculture with a focus on helping small farms.

Here are some facts and figures from Oxfam:

• One in six of the world's population is hungry
• Between 50 and 60 percent of childhood deaths in the developing world are hunger related
• The risk of death is 2.5 times higher for children with mild malnutrition than for children who are adequately nourished
• The proportion of overseas development assistance spent on agriculture has fallen from almost a fifth in 1980 to 3 percent today
• Poor people are particularly vulnerable to food price changes with many spending up to 80 percent of their income on food
• Even before the recent crisis 16,000 children died every day of hunger-related causes - one every five seconds

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