The death toll in Haiti's catastrophic earthquake could run to tens of thousands, the country's president said on Wednesday, a day after the quake demolished schools, hospitals, houses and hillside shanties across the crowded and improverished capital.
Asked by a CNN reporter how many people had died, President Rene Preval replied "I don't know", adding "up to now, I heard 50,000 ... 30,000".
But he did not say where these estimates came from.
Haitians wandered dazed in broken streets or tried to rescue people trapped under rubble. The local Red Cross said it was overwhelmed.
A five-story UN headquarters building was destroyed by Tuesday's 7.0 magnitude quake, which the US Geological Survey said was the most powerful in Haiti in more than a century. Several bodies were pulled from the wreckage of the UN building and more than 100 staff members were missing, a spokesman said.
The chief of the UN mission to Haiti, Hedi Annabi, was among those killed, Mr Preval said.
He said the damage was "unimaginable" and described stepping over dead bodies and hearing the cries of those trapped in the collapsed Parliament building, where the senate president was among those pinned by debris.
The UN said 14 people died when the headquarters collapsed. Susana Malcorra, a senior UN peacekeeping official, said 10 Brazilians, three Jordanians and one Haitian were confirmed to have died. UN peacekeeping chief Alain Le Roy said that the final number of UN deaths would almost certainly be much higher.
"The number of casualties and fatalities will be extremely high," he told reporters.
Destruction in the capital was "massive and broad," and tens - if not hundreds - of thousands of homes were destroyed, the UN mission said.
People sobbed in the streets of Port-au-Prince and voices cried out from the rubble.
The presidential palace lay in ruins, its domes fallen on top of flattened walls. Mr Preval and his wife were not inside when the quake hit.
The quake's epicentre was only 10 miles (16 km) from Port-au-Prince. About 4 million people live in the city and surrounding area. Many people slept outside on the ground, away from weakened walls, as aftershocks as powerful as 5.9 rattled the city throughout the night and into today.
The devastation crippled the government and the UN security mission that had kept order. There were no signs of organized rescue efforts, and people clawed at concrete chunks with their bare hands to try to free trapped loved ones.
Haitian Red Cross spokesman Pericles Jean-Baptiste said his organization was overwhelmed. "There are too many people who need help ... We lack equipment, we lack body bags," he said.
Normal communications were cut off, roads were blocked by rubble and trees, electric power was interrupted and water was in short supply.
The poorest country in the Western Hemisphere, Haiti is ill-equipped to respond to such a disaster, lacking heavy equipment to move debris and sufficient emergency personnel.
"I am appealing to the world, especially the United States, to do what they did for us back in 2008 when four hurricanes hit Haiti," Raymond Alcide Joseph, Haiti's ambassador to Washington, said in a CNN interview.
"At that time the U.S. dispatched ... a hospital ship off the coast of Haiti. I hope that will be done again ... and help us in this dire situation that we find ourselves in."
US president Barack Obama called the quake an "especially cruel and incomprehensible" tragedy and pledged swift, coordinated support to help save lives. The Pentagon was sending a nuclear-powered aircraft carrier and three amphibious ships, including one that can carry up to 2,000 Marines.
Medical aid group Medecins Sans Frontieres said its three hospitals in Haiti were unusable and it was treating the injured at temporary shelters.
"The reality of what we are seeing is severe traumas, head wounds, crushed limbs, severe problems that cannot be dealt with with the level of medical care we currently have available with no infrastructure really to support it," said Paul McPhun, operations manager for the group's Canadian section.
The University of Miami School of Medicine sent a plane full of doctors and nurses to set up a field hospital and planned to fly a group of critically injured people to Miami for treatment today.
The United Nations said $10 million would be released immediately from the its central emergency response fund and it would organize a flash appeal to raise more money for Haiti over the next few days.
The United States, China and European states were sending reconnaissance and rescue teams, some with search dogs and heavy equipment, while other governments and aid groups offered tents, water purification units, food and telecoms teams.
The quake hit at 5pm (2200 GMT), and witnesses reported people screaming and running into the streets as offices, hotels, houses and shops collapsed. Experts said the quake's epicenter was very shallow at a depth of only 6.2 miles (10km), which was likely to have magnified the destruction.
Witnesses saw homes and shanties built on hillsides tumble as the earth shook, while cars bounced off the ground. "You have thousands of people sitting in the streets with nowhere to go," said Rachmani Domersant, an operations manager with the Food for the Poor charity.
Haiti's cathedral was destroyed and media reports said the archbishop of Port-au-Prince, Monsignor Joseph Serge Miot, had been found dead in the wreckage of the archdiocese office.
In Geneva, UN officials said they expected the world body would issue an international emergency appeal for funds and other assistance, once needs on the ground had been assessed.
Germany was sending €1 million in immediate aid, and the EU's executive European Commission pledged €3 million of fast-track funding.
The United States, Britain, Canada, France, Belgium, Sweden, Luxembourg and Netherlands were sending reconnaissance and rescue teams, some with search dogs and heavy equipment, while other government and aid groups offered tents, water purification units, doctors and telecommunications teams.
Media reports said the archbishop of Port-au-Prince, Monsignor Joseph Serge Miot, has been found dead in the wreckage of the archdiocese office.
UN officials said normal communications had been cut off and the only way to talk with people on the ground was via satellite phone. Roads were blocked by rubble.
Some 9,000 UN police and troops are stationed in Haiti to maintain order and many countries were trying to determine the welfare of their personnel.
Reuters