PORT-AU-PRINCE: Aid workers hoping to distribute food, water and other supplies to a shattered Port-au-Prince are warning their efforts may need more security Friday as Haitians grow increasingly desperate and impatient for help.

United Nations peacekeepers patrolling the capital said people's anger is rising that aid hasn't been distributed quickly, and the Brazilian military warned aid convoys to add security to guard against looting.

"Unfortunately, they're slowly getting more angry and impatient," said David Wimhurst, spokesman for the Brazilian-commanded U.N. peacekeeping mission. "I fear, we're all aware that the situation is getting more tense as the poorest people who need so much are waiting for deliveries. I think tempers might be frayed."

The U.N. World Food Program reported Friday that its warehouses in the Haitian capital had been looted since Tuesday's cataclysmic earthquake. It didn't know how much of its pre-quake stockpile of 15,000 tons of food aid remained, but said some supplies were stored elsewhere in Haiti.

A spokeswoman for the Rome-based agency, Emilia Casella, noted that regular food stores in Port-au-Prince also had been emptied by looters.

Casella said the WFP was preparing shipments of enough ready-to-eat meals to feed 2 million Haitians for a month.

The international Red Cross estimated 45,000 to 50,000 people were killed in the quake Tuesday, based on information from the Haitian Red Cross and government officials. U.N. officials estimated Friday that 10 percent of the homes in Port-au-Prince had been destroyed, leaving some 300,000 people without shelter.

Hundreds of bodies were stacked outside the city morgue, and limbs of the dead protruded from the rubble of crushed schools and homes. A few workers were able to free people who had been trapped under the rubble for days, but others attended to the grim task of using bulldozers to transport loads of bodies.

For the long-suffering people of Haiti, the Western Hemisphere's poorest nation, shock was giving way to despair.

"We need food. The people are suffering. My neighbors and friends are suffering," said Sylvain Angerlotte, 22. "We don't have money. We don't have nothing to eat. We need pure water."

From Europe, Asia and the Americas, more than 20 governments, the U.N. and private aid groups were sending planeloads of high-energy biscuits and other food, tons of water, tents, blankets, water-purification gear, heavy equipment for removing debris, helicopters and other transport. Hundreds of search-and-rescue, medical and other specialists also headed to Haiti.

The WFP began organizing distribution centers for food and water Thursday, said Kim Bolduc, acting chief of the large U.N. mission in this desperately poor country. She said that "the risk of having social unrest very soon" made it important to move quickly.

Governments and government agencies have pledged about $400 million worth of aid, including $100 million from the United States.

But into the third day following the 7.0-magnitude quake, the global helping hand was slowed by a damaged seaport and an airport that turned away civilian aid planes for eight hours Thursday because of a lack of space and fuel.

Aid workers have been blocked by debris on inadequate roads and by survivors gathered in the open out of fear of aftershocks and re-entering unstable buildings.

"The physical destruction is so great that physically getting from point A to B with the supplies is not an easy task," Casella, the WFP spokeswoman, said at a news conference in Geneva.

Across the sprawling, hilly city, people milled about in open areas, hopeful for help, sometimes setting up camps amid piles of salvaged goods, including food scavenged from the rubble.

Small groups could be seen burying dead by roadsides. Other dust-covered bodies were being dragged down streets, toward hospitals where relatives hoped to leave them. Countless dead remained unburied, some in piles. Outside one pharmacy, the body of a woman was covered by a sheet, a small bundle atop her, a tiny foot poking from its covering.

Aid worker Fevil Dubien said some people were almost fighting over the water he distributed from a truck in a northern Port-au-Prince neighborhood.

Elsewhere, about 50 Haitians yearning for food and water rushed toward two employees wearing "Food For The Poor" T-shirts as they entered the international agency's damaged building.

"We heard a commotion at the door, knocking at it, trying to get in," said project manager Liony Batista. "'What's going on? Are you giving us some food?' We said, 'Uh-oh.' You never know when people are going over the edge."

Batista said he and others tried to calm the crowd, which eventually dispersed after being told food hadn't yet arrived.

"We're not trying to run away from what we do," Batista said, adding that coordinating aid has been a challenge. "People looked desperate, people looked hungry, people looked lost."

Engineers from the U.N. mission have begun clearing some main roads, and law-and-order duties have fallen completely to the mission's 3,000 international troops and police. About 5,500 U.S. soldiers and Marines were expected to be in Haiti by Monday. Their efforts will include providing security, White House spokesman Robert Gibbs said.

Wimhurst, the mission spokesman, said Haitian police "are not visible at all," no doubt because many had to deal with lost homes and family members. The first U.S. military units to arrive took on a coordinating role at the airport.

In Geneva, U.N. humanitarian spokeswoman Elisabeth Byrs said peacekeepers were maintaining security in Haiti despite the challenges.

"It's tense but they can cope," Byrs said. "Imagine those people who have not been eating or drinking for almost 50 hours and are already in a very poor situation, if they see a truck with something ... or if they see a supermarket which has collapsed, they just rush to get something to eat."

Batista, the Food For The Poor project manager, went back to the Dominican Republic late Thursday and awaited the arrival of 100 shipping containers loaded with rice, canned goods and building supplies.

"I don't think that a word has been invented for what is happening in Haiti," he said. "It is total disaster."