* Poor countries seen highly vulnerable to price gains
* U.N. expert blames speculation from traders for rises
GENEVA, Sept 7 (Reuters) - Riots over high bread prices in Mozambique and food shortages elsewhere should be a wake-up call for governments which papered over food security problems that arose two years ago, a United Nations expert warned on Tuesday.
"Donors have not delivered on their promises," Olivier De Schutter, the U.N. special rapporteur on the right to food, said during a mission to Syria.
"Most poor countries are still highly vulnerable. They continue to rely for their export revenues on a limited range of commodities, and their food security is excessively dependent on food imports whose prices are increasingly high and volatile." Almost 150 people were arrested in Mozambique after riots over a 30 percent rise in the price of bread, the result of soaring global wheat prices.
Egyptians have also protested over food prices and experts have warned that riots could break out in Africa and the Middle East.
De Schutter, noting that Syria was also affected by severe drought, said that increasing food and fuel prices hurt poorer countries most, especially those reliant on imports.
"Price increases are exacerbated by speculation from unregulated traders, and they are transmitted directly to households, who often spend 60 to 70 per cent of their incomes on food," he said.
Although the world cereal output in 2010 should still be the third highest on record, fears about future supplies have led the prices of wheat to increase 70 percent on international markets since last year, according to the United Nations. Much of the spike has been linked to drought and fires in Russia, which had been the world's No. 3 wheat exporter, and a decision by the Russian government to extend a grain export ban until late 2011.
De Schutter said overall food prices on international markets have already increased by five percent since July. A food price index by the Food and Agriculture Organisation, a U.N. agency, has hit its highest level since September 2008.
The FAO has called an emergency meeting for Sept. 24 in Rome for governments to confront weaknesses in the global food system and find ways to boost reserves. The U.N. expert said it was critical for donor countries to provide meaningful assistance.
"In 2008, many governments were taken by surprise," he said. "We have today a much better understanding of what needs to be done to realise the right to food." (Reporting by Laura MacInnis; Editing by Stephanie Nebehay and Noah Barkin)