Tensions rose among desperate Haitians awaiting international aid and hunting for missing relatives Saturday as aid began to trickle in four days after an earthquake that Haitian authorities say killed 200,000 people. On the other hand, a spokeswoman for the UN said that the earthquake in Haiti was the worst disaster ever confronted by the United Nations pointing out that the catastrophe has left affected regions with little infrastructure. “This is a historic disaster. We have never been confronted with such a disaster in the UN memory. It is like no other,” Elisabeth Byrs, spokeswoman of the UN Office for the Coordination of Humanitarian Affairs, said. She noted that at least local government structures remained after the 2004 tsunami hit Indonesia's Aceh province, but in Haiti, the town of Leogane, for example, had lost all its public services in the earthquake. Haiti's shell-shocked government gave the United States control over its main airport to bring order to aid and food flights from around the world and speed relief to the impoverished Caribbean nation. US Secretary of State Hillary Clinton was heading to Port-au-Prince Saturday to meet with Haitian President Rene Preval at the airport. Her plane was to bring in supplies and return with evacuated Americans. “We will also be conveying very directly and personally to the Haitian people our long-term unwavering support, solidarity and sympathies,” Clinton said. Trucks piled with corpses have been carrying bodies to hurriedly excavated mass graves outside the city, but thousands of bodies still are believed buried under rubble. “We have already collected around 50,000 dead bodies,” Interior Minister Paul Antoine Bien-Aime told Reuters. “We anticipate there will be between 100,000 and 200,000 dead in total, although we will never know the exact number.” Some 40,000 bodies had been buried in mass graves, said Secretary of State for Public Safety Aramick Louis. If the casualty figures turn out to be accurate, the 7.0 magnitude quake that hit Haiti Tuesday and flattened much of its capital city would be one of the 10 deadliest ever. Health Minister Alex Larsen told Reuters three-quarters of Port-au-Prince will have to be rebuilt. Three days after the quake, gangs of robbers had begun preying on survivors living in makeshift camps on streets strewn with debris and decomposing bodies, as aftershocks rippled through the hilly neighborhoods. Authorities reported some looting and growing anger among survivors despairing over the delay in life-saving assistance. Meanwhile, the United States and other nations rushed to deliver food, water and medical supplies through a jammed airport.