Rescuers continue to search for earthquake survivors

Tuesday's earthquake brought down buildings great and small - from shacks in shantytowns to President Rene Preval's gleaming white National Palace, where a dome tilted ominously above the manicured grounds.

Hospitals, schools and the main prison collapsed. The capital's Catholic archbishop was killed when his office and the main cathedral fell. The head of the UN peacekeeping mission was missing in the ruins of the organisation's multi-storey headquarters.

Police officers turned their pickup trucks into ambulances to carry the injured. Wisnel Occilus, a 24-year-old student, was wedged between two other survivors in a truck bed headed to a police station.

He was in an English class when the earth shook at 4.53pm local time and the building collapsed.

"The professor is dead. Some of the students are dead, too," said Mr Occilus, who suspected he had several broken bones. "Everything hurts."

Other survivors carried injured to hospitals in wheelbarrows and on stretchers fashioned from doors.

In Petionville, next to the capital, people used sledgehammers and their bare hands to dig through a collapsed shopping centre, tossing aside mattresses and office supplies. More than a dozen cars were entombed, including a UN truck.

Nearby, about 200 survivors, including many children, huddled in a theatre parking lot using sheets to rig makeshift tents and shield themselves from the sun in 90-degree heat.

"I can't take it anymore. My back hurts too much," said Alex Georges, 28, who was still waiting for treatment a day after his school collapsed and killed 11 classmates. A body lay a few feet away.

"This is much worse than a hurricane," said doctors' assistant Jimitre Coquillon. "There's no water. There's nothing. Thirsty people are going to die."

If there were any organised efforts to distribute food or water, they were not visible.

The aid group Doctors Without Borders treated wounded at two hospitals that withstood the quake and set up tent clinics elsewhere to replace its damaged facilities. Cuba, which already had hundreds of doctors in Haiti, treated injured in field hospitals.

Bodies were everywhere in Port-au-Prince: those of tiny children adjacent to schools; women in the rubble-strewn streets with stunned expressions frozen on their faces; men hidden beneath plastic tarps and cotton sheets.

Haiti's leaders struggled to comprehend the extent of the catastrophe - the worst earthquake to hit the country in 200 years - even as aftershocks reverberated.

"It's incredible," Mr Preval told CNN. "A lot of houses destroyed, hospitals, schools, personal homes. A lot of people in the street dead. ... I'm still looking to understand the magnitude of the event and how to manage."

Mr Preval said thousands of people were probably killed. Leading Senator Youri Latortue told The Associated Press that 500,000 could be dead, but conceded that nobody really knows.

"Let's say that it's too early to give a number," Mr Preval said.

As dusk fell, thousands of people gathered on blankets outside the crumpled presidential palace, including hundreds of women who waved their hands and sang hymns in a joyful, even defiant tone.

Ricardo Dervil, 29, said he decided to join the crowd because he was worried about aftershocks and was tired of seeing dead bodies.

"I was listening to the radio and they were saying to stay away from buildings," he said. "All I was doing was walking the street and seeing dead people."

Balancing suitcases and belongings on their heads, people streamed on foot into the Haitian countryside, where wooden and cinderblock shacks showed little sign of damage. Ambulances and UN trucks raced in the opposite direction, toward Port-au-Prince.

About 3,000 police and international peacekeepers cleared debris, directed traffic and maintained security in the capital.

But law enforcement was stretched thin even before the quake and would be ill-equipped to deal with major unrest. The UN's 9,000-member peacekeeping force sent patrols across the capital's streets while securing the airport, port and main buildings.

Looting began immediately after the quake, with people seen carrying food from collapsed buildings. Many lugged what they could salvage and stacked it around them as they slept in streets and parks.

Port-au-Prince's ruined buildings fell on both the poor and the prominent: The body of Archbishop Joseph Serge Miot, 63, was found in the ruins of his office, according to Fr Pierre Le Beller at Archbishop Miot's order, the Saint Jacques Missionary Centre in Landivisiau, France.

The United Nations said 16 UN personnel were confirmed dead and between 100 and 150 UN workers were still missing, including UN mission head Hedi Annabi of Tunisia and his chief deputy, Luis Carlos da Costa.

Senate President Kelly Bastien was rescued from the collapsed Parliament building and taken to a hospital in the neighbouring Dominican Republic. The president of Haiti's Citibank was also among the survivors being treated there, said Rafael Sanchez Espanol, director of the Homs Hospital in Santiago.

Even the main prison in the capital fell down, "and there are reports of escaped inmates," UN humanitarian spokeswoman Elisabeth Byrs said in Geneva.

Haiti seems especially prone to catastrophe - from natural disasters like hurricanes, storms, floods and mudslides to crushing poverty, unstable governments, poor building standards and low literacy rates.

Some of the biggest immediate health threats include respiratory disease from inhaling dust from collapsed buildings and diarrhoea from drinking contaminated water.

The international Red Cross said a third of the country's nine million people may need emergency aid, a burden that would test any nation and a crushing catastrophe for impoverished Haiti.