PORT-AU-PRINCE - US troops will help keep order on Haiti's increasingly lawless streets, the country's president said on Sunday as desperate earthquake survivors waited for food, water and medicine.

World leaders have pledged massive assistance to rebuild Haiti after the earthquake killed as many as 200,000 people, but five days into the crisis aid distribution was still random, chaotic and minimal.

Hundreds of thousands of hungry Haitians are waiting for help, many of them in makeshift camps on streets strewn with debris and decomposing bodies.

International medical teams took over damaged hospitals and clinics where wounded and sick people had lain untreated for days, in signs of a response to chronic shortages of doctors, surgeons, antiobiotics and pain killers.

International rescue teams raced against time to free survivors from the rubble of collapsed buildings in the wrecked capital, Port-au-Prince, but logistical logjams slowed the delivery of medical treatment and essential supplies for the wounded, hungry and homeless.

"This is one of the worst humanitarian crises in decades.

The damage, destruction, loss of life is just overwhelming," said UN Secretary General Ban Ki-moon, who visited the Haitian capital on Sunday.

With Haiti's overstretched police and UN peacekeepers unable to provide security and people turning more desperate by the day, hundreds of looters swarmed smashed shops in downtown Port-au-Prince in a second day of violence.

Looters fought each other with knives, hammers and rocks and police tried to disperse them with gunfire. At least one looter was shot dead, witnesses said.

Adding to the security fears, heavily armed gang members who once ran Haiti's worst slum like warlords have returned to the Cite Soleil shantytown since breaking out from prison after the 7.0 magnitude earthquake struck on Tuesday.

President Rene Preval said 3,500 US troops would be deployed to help UN and Haitian forces restore security in the capital.

"We have 2,000 police in Port-au-Prince who are severely affected. And 3,000 bandits escaped from prison. This gives you an idea of how bad the situation is," Preval told reporters.

But US military officials declined to comment on details of their role or the rules of engagement.

Though a few street markets had begun selling vegetables and charcoal, businessmen and bank owners were demanding more security in order to reopen.

Thieves lynched

Residents awoke to find the bodies of thieves lynched by mobs or shot by men claiming to be plainclothes police. A Reuters journalist saw the burned body of a man locals said was set ablaze by angry residents who caught him stealing, and two young men lying on the ground with bullet wounds to the head and arms tied behind their backs.

"Haitians are partly taking things into their own hands.

There are no jails, the criminals are running free, there are no authorities controlling this," said teacher Eddy Toussaint, part of a crowd staring at the bodies.

Many people streamed out of the city over the weekend, on foot with suitcases on their heads or jammed in cars, to find food and shelter in the countryside.

Others crowded the airport hoping to get on planes that arrived laden with emergency supplies and left packed with Haitians. The shell-shocked government has given the US military control over the tiny airport to guide aid flights from around the world.

Dozens of nations have sent planes with rescue teams, doctors, field hospitals, food, medicine and other supplies, but faced a bottleneck at the airport, where fuel was scarce.

Some groups complained that their flights were diverted to the neighboring Dominican Republic, forcing them to carry emergency supplies into Haiti overland.

"The challenge at this time is how to coordinate all of this outpouring of assistance," said Ban, adding that the United Nations was feeding 40,000 people a day and hoped to increase that to 1 million within two weeks.

Scrums for food

Hundreds of trucks carrying aid and guarded by armed UN patrols streamed away from the airport and UN headquarters to different parts of the city but they were soon obstructed on streets clogged with people, debris, and vans carrying coffins and bodies.

There were jostling scrums for food and water as US military helicopters swooped down to throw out boxes of water bottles and rations. A reporter also saw foreign aid workers tossing packets of food to desperate Haitians.

"The distribution is totally disorganized. They are not identifying the people who need the water. The sick and the old have no chance," said Estime Pierre Deny, standing at the back of a crowd looking for water with his empty plastic container.

Haiti is the Western Hemisphere's poorest country and has for decades struggled with devastating storms, floods and political unrest. Around 9,000 UN peacekeepers have provided security since a 2004 uprising ousted one president, but the mission lost at least 40 members when its headquarters collapsed, including its top leaders.

More rescued alive

Aftershocks still shook the capital, terrifying survivors and sending rubble and dust tumbling from buildings.

Three people were pulled out alive from a collapsed supermarket early on Sunday. US and Turkish teams freed a young Haitian girl, a Haitian man and an American woman from the rubble of the five-story building. They were dazed but did not appear to be seriously injured.

Trucks piled with corpses were ferrying bodies to hurriedly excavated mass graves outside the city, but tens of thousands of bodies are still believed buried under the rubble.

Haitian government officials said the death toll was likely to be between 100,000 and 200,000.

Dozens of bloated bodies were decomposing in the sun outside the main hospital and its gardens were a mass of beds with injured people, with makeshift drips hanging from trees.

Haiti's government is struggling to operate as the quake destroyed the presidential palace and knocked out communications and power. Preval is living at the judicial police headquarters and holding cabinet meetings with foreign ambassadors outside, seated on a circle of plastic chairs.

"Everything in Haiti is broken. There is not one person in the country without a friend or family member dead," said Information Minister Marie Laurence Jocelyn Lassegue. "When they say the government is not fast, we are truly doing our best."

¬