(Adds details on meeting, demonstrations)

By Sylvia Westall

VIENNA, April 25 (Reuters) - Rising food prices have developed into a global crisis, United Nations Secretary-General Ban Ki-moon said on Friday.

Concerns about food security mounted this week as rice prices hit records in Asia and the United States warned that staples for the world's hungry were getting much more expensive.

"This steeply rising price of food has developed into a real global crisis," Ban told journalists in Vienna.

Anger over high food and fuel costs in recent months has sparked protests in several countries.

In Haiti, the poorest country in the Americas, protests have brought down the government and killed six, while in Cameroon at least 24 have died in protests linked partly to rising living costs.

Governments of several food-growing countries, worried about domestic shortages, have imposed export curbs, spooking markets at a time when world inventories are down sharply.

Ban said the crisis would be discussed at a meeting of U.N. agency heads, the World Bank and the International Monetary Fund on April 28-29 in Berne, Switzerland.

"The United Nations is very much concerned as all members of the international community (are)," he said. "We must take immediate action in a concerted way."

Ban said world leaders should discuss ways to improve food distribution systems and production.

Japan announced $100 million in emergency food aid on Friday and World Food Program's executive director said on Thursday the cost of feeding the world's hungry had spiked nearly 40 percent amid spiralling food costs and oil prices.

International Monetary Fund has said it is in talks with governments in 10 countries, mostly in Africa, about increasing financial assistance to cover the soaring cost of food.

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