Thousands of Haitians spent a third night without shelter or in makeshift camps in Haiti's ruined capital, after the Caribbean country was hit by its worst earthquake in 200 years.
Aid has been arriving from around the world, but correspondents are reporting a growing frustration in Port-au-Prince over delays in its distribution.
In one part of the city, angry Haitians reportedly blocked streets with corpses to demand quicker relief efforts. There were also reports of looting and gunshots.
"All of my family died -- my niece, my sister, my aunt and my mother. My house is destroyed. I don't have anywhere to live, all the people here don't have anywhere to live," one quake survivor said. "I want to know what the government here is going to do."
Paul Garwood, of the World Health Organization (WHO), said the scale of the disaster has "overwhelmed all capacity," adding that this included body bags.
Aid groups say clean water, food, and medical supplies are desperately needed for the survivors.
Vincent Hoedt, who works at the emergency department for Doctors Without Borders (MSF) in Amsterdam, told RFE/RL that doctors are struggling to treat the vast numbers of injured.
"Our people had to start doing initial wound care in makeshift places, in offices, in tents, in empty buildings," Hoedt said.
"Now we are shifting our work to other hospitals that are still standing, but where the medical staff from the Haitian Ministry of Health had abandoned because they had to flee for their lives and to look after their family members."International Mobilization
The International Red Cross estimates that up to 45,000-50,000 people were killed in the 7.0-magnitude quake on January 12, which flattened much of Port-au-Prince.
The United Nations says some 3.5 million people in Haiti -- the poorest country in the Western Hemisphere -- live in areas affected by the quake. It also says about 300,000 people have been left homeless by the earthquake, which destroyed one in 10 homes in Port-au-Prince.
Teams from the United States, Europe, Russia, China, Canada, and Latin America have arrived and begun to distribute aid, conduct rescue operations with heavy lifting gear and dogs, and attend to the vast medical needs.
In Washington, U.S. President Barack Obama said he assured Haitian President Rene Preval -- who himself was left homeless by the earthquake -- that the United States will do everything to help the victims.
"As the international community continues to respond, I do believe that America has a continued responsibility to act," Obama said. "Our nation has a unique capacity to reach out quickly and broadly and to deliver assistance that can save lives."
Obama said he will meet on January 16 with former presidents Bill Clinton and George W. Bush, who he has enlisted to help raise relief money.
At the Pentagon, U.S. Defense Secretary Robert Gates said the United States expects to have between 9,000 and 10,000 troops in Haiti, though he stressed that most of them would be crew members of several warships, not those directly involved in the relief effort.
In New York, UN Emergency Relief Coordinator John Holmes said the international community is mobilizing "with all possible speed" to get the aid to Haiti "as quickly as possible."
"Local medical infrastructure is both badly damaged and overwhelmed by the number of injuries, so again, that is a top priority to get more doctors in there, more medical teams, field hospitals, more medical supplies to make sure we can tackle that problem," Holmes said.
"After that, of course there are the basic issues of water, I think that's going to be a major challenge too, I think that's clear from all we are hearing on the ground, food and emergency shelter as time goes on."Mounting Frustration
More than 48 hours after disaster struck, bodies piled up on the streets of Port-au-Prince and bulldozers were being used to remove the dead, but there were reports of mounting frustration and anger.
Shaul Schwarz, a photographer for "Time" magazine, said he saw at least two downtown roadblocks formed with bodies of earthquake victims and rocks. He told Reuters, "People are fed up with getting no help."
Correspondents say there is little sign of help beyond the airport, with bottlenecks and infrastructure damage holding up aid efforts.
And rescue teams and supplies are facing problems just getting into Haiti. The country's main port has been heavily damaged, making delivery of aid by sea difficult.
Planes queued to land at Port-au-Prince's small airport's tarmac and single runway, which AP reported was short of jet fuel and ramp space and without a control tower. The news agency said one relief organization had three charter planes turned back.
Hoedt said MSF staff and cargo had to find alternative way to get to Port-au-Prince.
"We had people coming via Miami who managed to come in with small airplanes that could negotiate access. And we're sending a lot of people via the Dominican Republic, who then try to make their way over land by taxi and buses to reach Port-au-Prince," Hoedt said.
"Also, we have been successful, just a few hours ago, to get the first cargoes landing already at Port-au-Prince's airport."
Adding to the logistical problems, there were reports of widespread insecurity, with AFP new agency reporting that sporadic gunshots could be heard.
The UN World Food Program (WFP) initially said its warehouses in the Haitian capital have been looted, though the agency later said the reports were exaggerated and that it still had food stocks..
But spokeswoman Emilia Casella said the WFP was still preparing emergency food rations.
"People are unable to cook and so what they need right now is ready-to-eat foods," Casella said, adding that the WFP hopes to reach about 2 million people affected by the quake with an emergency operation that will "start by calling for 14 million humanitarian daily rations" -- enough to feed 2 million people for about 30 days.
U.S. Defense Secretary Gates acknowledged that there has been some "minor scavenging" by Haitians trying to find food and water, but he said U.S. military leaders report that the country's security situation is satisfactory, given the extreme circumstances.
"The key is to get the food and the water in there as quickly as possible so that people don't, in their desperation, turn to violence or lead to the security situation deteriorating, and that's why there's such a high priority now in getting food and water in to people," Gates said. "But at this point, other than some scavenging and minor looting, our understanding is the security situation's pretty good."
The United Nations was launching an emergency appeal for about $550 million to help survivors.
The UN says over $268 million has been pledged by organizations and governments around the world to help the humanitarian rescue efforts. Both the United States and World Bank have promised $100 million.with agency reports