GENEVA (AFP) - Soaring food prices are causing logistical headaches for aid agencies committed to fighting hunger, not least the World Food Programme -- known to many as the granary of the United Nations.

"We distribute four million tonnes of supplies each year, so the 55 percent rise in food prices since June 2007 has an enormous impact on our operations," WFP spokeswoman Christiane Berthiaume told AFP.

Two million tonnes are bought by the WFP in regional markets while the rest is funded by donor countries.

Basic foodstuff prices have all risen sharply in recent months, sparking violent protests in many countries, including Egypt, Cameroon, Ivory Coast, Mauritania, Ethiopia, Madagascar, the Philippines and Indonesia.

The WFP feeds 73 million people in 78 different countries but has found it harder to procure supplies amid rising costs and government intervention in food exports.

"It has become very difficult to find food," said Nicole Menage, head of the WFP's food purchasing service at its Rome headquarters. "Many countries have introduced limits on food exports, in Asia, Africa and Latin America."

"For us, the challenge is to strike a balance between getting enough supplies without jeopardising the food security of these countries," Menage added.

Soaring food supplies are not the WFP's only headache though. In West Africa, its operational costs have risen 30 percent due to higher oil prices and their impact on transport costs.

Last November, WFP executive director Josette Sheeran warned West Africa faced a "perfect storm" crisis amid climate change, rising food prices and population growth.

The organisation launched an additional appeal for 500 million dollars (325 million euros) to help cover its costs.

Many WFP donors attach conditions to their support -- for example, Japan and Canada insist that the money they give be used to buy food from Japanese and Canadian farmers, Berthiaume said.

Similarly, the United States provides the vast majority of its aid in food rather than money, meaning they can curb their agricultural surplus but keep subsidising farmers, according to Mickey Chopra of the Medical Research Council in Cape Town, South Africa.

These factors combine to put African and other developing nations at a twofold disadvatage.

"The agricultural surplus that the US gives to the WFP first all of led to lower food prices in Africa, and then to a lack of investment in the agriculture sector in these countries," Chopra told AFP.

This means African countries are now unable to take full advantage of booming food prices because their agricultural infrastructure is in such a poor state, he said.

Chopra called on the WFP to invest in local food production in Africa and to provide countries with the necessary technical assistance.

Thirty-seven countries currently face food crises, the Rome-based Food and Agriculture Organisation said in its latest Crop Prospects and Food Situation Report last week.

"In the face of food riots around the world like in Africa and Haiti, we really have an emergency," FAO head Jacques Diouf said, adding the matter was worthy of attention by the UN Security Council.

"I'm surprised I have not been summoned to the UN Security Council, since many problems discussed there do not have the same consequences for peace and security in the world and the human rights of people who need to be fed," Diouf told a news conference in Rome.