An Air China plane carrying a Chinese search-and-rescue team, medics and tons of food and medicine landed at Port-au-Prince airport before dawn, along with three French planes with aid and a mobile hospital, officials said. A British relief team arrived in neighboring Dominican Republic.
The U.S. and other nations said they were sending food, water, medical supplies to assist the Western Hemisphere's poorest nation, where the international Red Cross estimated 3 million people -- a third of the population -- may need emergency relief.
In the streets of the capital, survivors set up camps amid piles of salvaged goods, including food being scavenged from the rubble.
"This is much worse than a hurricane," said Jimitre Coquillon, a doctor's assistant working at a makeshift triage center set up in a hotel parking lot. "There's no water. There's nothing. Thirsty people are going to die."
If there were any organized efforts to distribute food or water, they were not visible Wednesday.
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.
President Barack Obama promised an all-out rescue and humanitarian effort including the military and civilian emergency teams from across the U.S. The aircraft carrier USS Carl Vinson was expected to arrive off the coast Thursday and the Navy said the amphibious assault ship USS Bataan had been ordered to sail as soon as possible with a 2,000-member Marine unit.
"We have to be there for them in their hour of need," Obama said.
A U.S. military assessment team was the first to arrive, to determine Haiti's needs.
French Foreign Minister Bernard Kouchner said the French three planes that touched down Thursday are to evacuate around 60 injured people to hospitals in the Caribbean islands of Martinique and Guadeloupe. He told France Inter radio two additional French relief planes are on their way.
There was no estimate on how many people were killed by Tuesday's magnitude-7 quake. Haitian President Rene Preval said the toll could be in the thousands. Leading Sen. Youri Latortue told The Associated Press the number could be 500,000, but conceded that nobody really knew.
"Let's say that it's too early to give a number," Preval said told CNN.
Survivors used sledgehammers and their bare hands to try to find victims in the rubble. In Petionville, next to the capital, people dug through a collapsed shopping center, tossing aside mattresses and office supplies. More than a dozen cars were entombed, including a U.N. truck.
Nearby, about 200 survivors, including many children, huddled in a theater parking lot using sheets to rig makeshift tents and shield themselves from the sun in 90-degree heat.
Police officers carried the injured in their pickup trucks. 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 magnitude-7 quake struck at 4:53 p.m. and the building collapsed.
"The professor is dead. Some of the students are dead, too," said Occilus, who suspected he had several broken bones. "Everything hurts."
Other survivors carried injured to hospitals in wheelbarrows and on stretchers fashioned from doors.
Bodies lay everywhere in Port-au-Prince: tiny children next to schools, women in rubble-strewn streets with stunned expressions frozen on their faces, men hidden beneath plastic tarps and cotton sheets.
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 U.N. trucks raced in the opposite direction, toward Port-au-Prince.
Calls from victims seeking help from emergency services weren't getting through because systems that connect different phone networks were not working, said officials from a telecommunications provider in Haiti.
Calls were being placed sometimes 15 to 20 times from the same phone, which was "painful to watch," said Jyoti Mahurkar-Thombre, Alcatel-Lucent's general manager of wireless voice.
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 U.N.'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. Inmates were reported to have escaped from the damaged main prison in Port au Prince, said Elisabeth Byrs, a U.N. humanitarian spokeswoman in Geneva.
It was unclear whether the U.S. ground troops heading this way would be used for security operations as well as humanitarian efforts.
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, said the Rev. Pierre Le Beller at Miot's order, the Saint Jacques Missionary Center in Landivisiau, France.
Haitian Senate President Kelly Bastien was rescued from the collapsed Parliament building and taken to a hospital in the neighboring 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.
A U.S. Coast Guard helicopter evacuated four critically injured U.S. Embassy staff to the hospital at the U.S. naval base at Guantanamo Bay, Cuba, where the military has been detaining suspected terrorists.
The U.S. Embassy had no confirmed reports of deaths among the estimated 40,000 to 45,000 Americans who live in Haiti, but many were struggling to find a way out of the country.
The International Committee of the Red Cross said Thursday it has launched a Web site to help Haitians find loved ones missing in the quake.
Robert Zimmerman, deputy head of the group's tracing unit, said people in Haiti and abroad can use the site to register the names of missing relatives.
As dusk fell Wednesday, 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."
How to help victims of the Haiti earthquake
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