PORT-AU-PRINCE, Haiti (CNN) — The powerful Haitian earthquake destroyed most of the capital city of Port-au-Prince, a teeming hillside city where toppled buildings have killed and injured an untold number of people and trapped others in the rubble, Haitian authorities said Wednesday.
Haiti's ambassador to the United States, Raymond Joseph, called it a "major catastrophe," and he said the first lady, Elisabeth Debrosse Delatour, reported that "most of Port-au-Prince is destroyed" and that many government buildings had collapsed.
Joseph said the National Palace, which he called a "steady building," and several government ministries had collapsed. "But a silver lining in all of that is that the earthquake hit after closing hours. So most of the employees of the state were already out of the buildings."
U.N. Secretary-General Ban Ki-moon also reported "a devastating impact" on Port-au-Prince, but said the remaining areas of Haiti appear to be largely unaffected.
Rescue crews were racing Wednesday morning to fully assess the heavily damaged buildings and infrastructure across the capital and what Ban Ki-moon described as the collapse of "basic services such as water and electricity."
One in three people in Haiti -- about 3 million people -- were affected by the quake, the Red Cross estimated. The U.S. State Department has been told to expect "serious loss of life," spokesman P.J. Crowley said, though precise casualty estimates were not immediately available. The U.N.'s Ban said the casualties may well be in the hundreds."
CNN's Anderson Cooper, viewing Port-au-Prince from a helicopter, called the sight of the destroyed buildings in the quake-devastated city "incredibly shocking" and "eerie."
He said many people are "just kind of standing around on the streets, not really sure what to do or where to go, and for many, there is nowhere to go."
The earthquake sheared huge slabs of concrete off structures and pancaked scores them, trapping people inside those buildings, and knocking down phone and power lines. Many buildings that remained standing were left open to the elements, pictures from the scene showed, and citizens were dusty from the concrete and in some cases bloody from their injuries.
Travel agent Jacqualine Labrom spotted a collapsed church and leveled dwellings and noted that some people were in a "state of hysteria," perhaps because they had never seen an earthquake of this magnitude in their lives.
At God's Littlest Angels orphanage, on the mountainside above Port-au-Prince, children and staff slept outside Tuesday, enduring aftershocks well into the night.
The earthquake "knocked down people, kids, the food off the stove for supper, all of my glassware out of the cabinet," Dixie Bickel, who runs the orphanage, wrote on its Web site. "The children are sleeping outside in the drive. Even our little babies are outside tonight!"
First rescuers on the scene were often local people trying to help dig people out of the rubble by hand, or to comfort injured survivors. Clay Cook told CNN that his daughter, who works at a mission in Haiti, was briefly trapped at home after the quake. Three staff workers and her husband managed to free her from the concrete, he said.
The powerful 7.0-magnitude earthquake struck shortly before 5 p.m. ET Tuesday, centered about 10 miles (15 km) southwest of Port-au-Prince, the U.S. Geological Survey reported. It could be felt strongly in eastern Cuba, more than 200 miles away.
Ban said the U.N. headquarters at the Christopher Hotel collapsed in the quake, and that people are still trapped inside. He said possibly 100 or 150 people were in the building around the time the quake struck. He said the chief of the U.N. mission in Haiti and a deputy special representative have not been accounted for.
At least four U.N. peacekeepers were reported to have been killed. Three Jordanian peacekeepers died, according to Jordan's state-run Petra News Agency, and the Argentine military confirmed the death of a U.N. peacekeeper from Argentina.
U.S. officials said aircraft had been sent on a reconnaissance mission to determine the state of the international airport in Port-au-Prince. Joseph said it appears that the airport was not damaged. Though the tower is down, he said, the runway is usable.
The quake had reportedly damaged The Hotel Montana, popular with foreigners visiting Port-au-Prince. French Minister of Cooperation Alain Joyandet expressed concern Wednesday for the approximately 200 French tourists staying there.
The United States and global humanitarian agencies said they would to begin delivering much-needed aid Wednesday amid fears that impoverished Haiti, already inflicted with human misery, was facing nothing short of a catastrophe.
"This is obviously a tremendous tragedy that happened just before sundown last night," Rajiv Shah, administrator of the U.S. Agency for International Development, told CNN Wednesday.
"Our teams have been working in a coordinated and aggressive way all night to make sure the U.S. mounts an effective response in supporting saving lives, which is the president's absolute top priority for this first period of 72 hours when we search and save as many lives as we can."
The United States was the first to offer help after the quake hit Haiti, Joseph said, and many countries and agencies across the globe geared up to help the country. Ban said the U.N. plans to release $10 million in aid immediately.
Adm. Michael Mullen, chairman of the U.S. Joint Chiefs of Staff said the United States plans to do all it can to help. U.S. officials say the USNS Comfort, a Naval hospital ship, in port in Baltimore has begun to recall its crew and is standing by for orders to head to Haiti. U.S. Coast Guard ships are en route to the scene.
The disaster is the latest to befall the country of about 9 million people, roughly the size of Maryland, which is the poorest in the Western hemisphere and among the poorest in the world.
Hurricane Gordon killed more than 1,000 people in 1994, while Hurricane Georges killed more than 400 and destroyed most of the country's crops in 1998. And in 2004, Hurricane Jeanne killed more than 3,000 people even as it passed north of Haiti, with most of the deaths in the northwestern city of Gonaives. That city was hit heavily again in 2008, when four tropical systems passed through.