A demonstrator smashes the windows of an airline office in Port-au-Prince, Tuesday, April, 8, 2008. Hungry Haitians stormed the presidential palace Tuesday, throwing rocks and demanding the resignation of President Rene Preval over soaring food prices. Overwhelmed guards struggled to hold back the crowd until U.N. peacekeepers came to their rescue, firing rubber bullets and tear gas.(AP Photo/Jack Tierney)Haitians run through the streets during demonstrations April 8 in Port-au-Prince against the cost of living in Haiti. Blue-helmet UN peacekeepers were called in Tuesday to protect Haiti's presidential palace after violent demonstrations against high food and fuel prices broke out in the capital.(AFP/Thony Belizaire)By JONATHAN M. KATZ, Associated Press Writer PORT-AU-PRINCE, Haiti - Hungry Haitians stormed the presidential palace Tuesday to demand the resignation of President Rene Preval over soaring food prices and U.N. peacekeepers battled rioters with rubber bullets and tear gas.Rioters were chased away from the presidential palace but by late afternoon had left trails of destruction across Port-au-Prince. Concrete barricades and burned-out cars blocked streets, while windows were smashed and buildings set on fire from the capital's center up through its densely populated hills.Outnumbered U.N. peacekeepers watched as people looted businesses near the presidential palace, not budging from the building's perimeter. Nearby, but out of sight of authorities, another group swarmed a slow-moving car and tried to drag its female driver out the window."We are hungry! He must go!" protesters shouted as they tried to break into the presidential palace by charging its chained gates with a rolling dumpster. Moments later, Brazilian soldiers in blue U.N. helmets arrived on jeeps and assault vehicles, firing rubber bullets and tear gas canisters and forcing protesters away from the gates.Food prices, which have risen 40 percent on average since mid-2007, are causing unrest around the world. But nowhere do they pose a greater threat to democracy than in Haiti, one of the world's poorest countries where in the best of times most people struggle to fill their bellies."I think we have made progress in stabilizing the country, but that progress is extremely fragile, highly reversible, and made even more fragile by the current socio-economic environment," U.N. envoy Hedi Annabi said Tuesday after briefing the Security Council.For months, Haitians have compared their hunger pains to "eating Clorox" because of the burning feeling in their stomachs. The most desperate have come to depend on a traditional hunger palliative of cookies made of dirt, vegetable oil and salt.Riots broke out in the normally placid southern port of Les Cayes last week, quickly escalating as protesters tried to burn down a U.N. compound and leaving five people dead. The protests spread to other cities, and on Monday tens of thousands took to the streets of Port-au-Prince.The U.S. Embassy in Haiti warned American citizens in the chaotic capital to avoid crowds and roadblocks and to remain vigilant. Embassy buildings were pelted with rocks on Tuesday but there have been no reports of injuries to U.S. citizens.Preval, a soft-spoken leader backed by Washington, was at work in the palace during the protests, aides said. He has made no public statements since the riots began."I compare this situation to having a bucket full of gasoline and having some people around with a box of matches," said Preval adviser Patrick Elie. "As long as the two have a possibility to meet, you're going to have trouble."The protesters also are demanding the departure of the 9,000 U.N. peacekeepers, whom they blame in part for rising food prices. The peacekeepers came to Haiti in 2004 to quell the chaos that followed the ouster of former President Jean-Bertrand Aristide.They helped usher in a democratic transition, but critics say both Preval and the international community have focused too much on political stability without helping to alleviate poverty. That could spell trouble not only for Preval, but for Haiti's fragile democracy as well."We voted Preval for a change. Nothing happened," said Joel Elie, 31, who like many Haitians is unemployed. "We're tired of it and we can't wait anymore."While the peacekeepers spend more than US$500 million (euro320 million) a year in Haiti, the World Food Program has collected less than 15 percent of the US$96 million (euro61 million) it says Haiti needs in donations this year. The WFP issued an emergency appeal Monday for more.Meanwhile, new customs procedures aimed at collecting revenues and stopping the flow of drugs has left tons of food rotting in ports, especially in the country's north. In a country where almost all food is imported, cargo traffic from Miami ground nearly to a halt, though shippers say intervention by Preval last month has improved the situation somewhat.Government officials say the riots are being manipulated by outside forces, specifically drug smugglers who can operate more easily amid chaos and supporters of Guy Philippe, a fugitive rebel leader wanted in U.S. federal court in connection with a drug indictment.Annabi, the U.N. envoy, said "people with political motivations" were exploiting the demonstrations, but didn't say who he was referring to.Many in the crowds are demanding the return of the exiled Aristide, and thousands showed up Monday for a rally by a key Aristide ally, the Rev. Gerard Jean-Juste, in the oceanside slum of Cite Soleil.___Associated Press writer Evens Sanon contributed to this report.