Robert Zoellick

World Bank President Robert Zoellick is warning that high food prices could wipe out hard-won gains against poverty and malnutrition.

Zoellick says in a new World Bank report issued Wednesday that people in poor urban areas and low-income countries are suffering daily from the impact of high prices.

The report said the price of wheat in Yemen has doubled in the past year and could reverse all the gains made in poverty reduction made in the past 10 years in the country.

Also Wednesday, the head of the United Nations Food and Agriculture Organization, Jaques Diouf, warned rising commodity prices could spark more food riots.

Diouf told a forum in New Delhi that food prices have jumped 45 percent in the last nine months and that there are "serious shortages" of rice, wheat, and maize.

Food riots have already erupted in Haiti, Egypt, Cameroon, Burkina Faso, and Senegal.

Diouf warned the chance for more riots is high in developing nations where people spend as much as 60 percent of their income on food.

The U.N. and World Bank blame the rising cost of food on a combination of factors, including climate change, increased demand for biofuels, and higher energy prices. Both organizations are calling on the international community to invest in rural infrastructure to help ease food shortages.