June 4 (Bloomberg) -- Governments need to invest $15 billion to $20 billion a year to tackle the food crisis that's seen prices rise around the world, triggering riots in some countries, United Nations Secretary-General Ban Ki-moon said.

``We must focus on the underlying causes: years of neglect of the agricultural sector and the lack of investment in increasing productivity,'' Ban told reporters at the World Food Summit in Rome. `` The price of oil has contributed significantly in the price rise of food. There is no doubt about that it affected the cost of transportation.''

Delegates at the three-day summit, including more than 30 heads of state, have gathered to discuss the causes and solutions for an increase in crop prices over the past two years that threatens to swell the ranks of the world's more than 800 million hungry people. The UN World Food Programme today announced today it will disburse an extra $1.2 billion a year toward helping 75 million of the world's starving population.

``With soaring food and fuel prices, hunger is on the march and we must act now,'' said Josette Sheeran, executive director of the World Food Programme, told delegates today.

More aid money is rolling in. The International Development Bank today pledged $1.5 billion in food aid over the next five years, the UN Food and Agriculture Organization, the conference organizer, said today.

``We don't have clear evidence on the trade-off between agriculture products and biofuels,'' Ban said. There is an ``urgent need to establish an international consensus and agreed policy guidelines,'' he said.

-- With reporting by Andrew Davis and Flavia Krause-Jackson in Rome. Editors: Kristen Hallam, Todd White

To contact the reporter on this story: Alex Morales in Rome at amorales2@bloomberg.net;

Last Updated: June 4, 2008 05:25 EDT