Global food prices fell sharply in May, dropping 4% from the previous month to their lowest level since September 2011, the UN Food and Agricultural Organization has said.

The FAO's Food Price Index, a monthly measure of changes in a basket of food commodities, was nine points lower at 204 points, a statement said.

That was "due to generally favourable supplies, growing global economic uncertainties and a strengthening of the US dollar," it added.

"Crop prices have come down sharply from their peak level but they remain still high and vulnerable due to risks related to weather conditions in the critical growing months ahead," FAO grain analyst Abdolreza Abbassian was quoted as saying.

Meanwhile, the organization raised its forecast for global cereal production by 48.5 million tonnes, mainly on the expectation of a bumper maize crop in the United States.

The FAO now expects 2012 output to set a record of 2.419 billion tonnes, which would be 3.2% higher than the 2011 record.

"However, with planting still to be completed and much of the crop at very early stages of development, the final outcome will depend greatly on weather conditions in the coming months," the agency noted.

On May 30, the FAO warned that one in seven people worldwide suffer from malnutrition in a report released ahead of a summit on sustainable development to be held in Rio de Janeiro June 20-22.

An FAO report called on governments to invest in infrastructure and protect the rights of the poor to food resources.

Three quarters of the world's poor live in rural areas and most of them depend on agriculture and related activities for their livelihoods, it said.