Global food prices fell sharply last month as production increased in key crop producing regions, but economic turmoil is expected to hit the poor in developing countries, the UN food agency said on Thursday.

The Rome-based Food and Agriculture Organisation (FAO) said its monthly food price index fell by two percent in September compared to August, to 225 points. That was substantially lower than the record high of 238 points reached in February 2011.

"International prices of all cereals with the exception of rice fell sharply," FAO said, adding that higher production had combined with lower than expected demand including for ethanol, which had helped push up cereal prices.

The index was still higher than its September 2010 value of 195 points however.

The FAO also forecast that world cereal production would total 2.3 billion tonnes this marketing season -- three percent higher than in 2010/2011 -- including a 4.6 percent rise in global wheat production, mainly due to Black Sea supplies.

"Despite the expected production gains, the report warns that because of the slowdown in the global economic recovery and increased risks of recession, there is uncertainty as regards the impact on world food security," FAO said.

It also warned that the situation remained dire in the drought-hit Horn of Africa and that 750,000 people were at risk of death in the region.

But it added that aid efforts "should start to improve the situation later in the year."

It also said that irregular rains could affect crop prospects in West Africa.

Monsoons in Far East Asia including Bangladesh, India, Pakistan, Thailand and the Philippines could also lower production in several countries.