Haitians piled the bodies of their friends and neighbours along the streets of their devastated capital as rescuers were forced to dig through the rubble with their bare hands.

Haitians have piled bodies along the devastated streets of their capital after a powerful earthquake crushed thousands of structures yesterday, from schools and shacks to the National Palace and the UN peacekeeping headquarters. Untold numbers were still trapped.

It seemed clear that the death toll from Tuesday (Wednesday, NZT) afternoon's magnitude-7.0 quake would run into the thousands, with the country's prime minister estimating it could be as high as 100,000.

The chief of the UN mission in Haiti, Hedi Annabi, was among the dead, Haitian President Rene Preval said.

"Ambassador Annabi died. We send our sympathy and condolences to all the international community," Preval told journalists in Port-au-Prince.

UN Secretary-General Ban Ki-moon had said earlier he could not confirm reports Annabi had died.

The Roman Catholic archbishop of Port-au-Prince was also among the victims.

International Red Cross spokesman Paul Conneally said a third of Haiti's 9 million people may need emergency aid and that it would take a day or two for a clear picture of the damage to emerge. The United Nations said the capital's main airport was "fully operational" and that relief flights would begin today.

Aftershocks continued to rattle the capital of 2 million people as women covered in dust clawed out of debris, wailing. Stunned people wandered the streets holding hands. Thousands gathered in public squares to sing hymns.

People pulled bodies from collapsed homes, covering them with sheets by the side of the road. Passersby lifted the sheets to see if loved ones were underneath. Outside a crumbled building the bodies of five children and three adults lay in a pile.

The promiment died along with the poor: the body of Archbishop Joseph Serge Miot, 63, was found in the ruins of his office, said Father Pierre Le Beller of the Saint Jacques Missionary Center in Landivisiau, France. He told The Associated Press by telephone that fellow missionaries in Haiti told him they found Miot's body.

The United States and other nations - from Iceland to Venezuela - said they would start sending aid workers and rescue teams to Haiti the start of a major emergency operation. The international Red Cross and other aid groups announced plans for major relief operations in the Western Hemisphere's poorest country.

Many will have to help their own staff as well as stricken Haitians. Taiwan's Foreign Ministry said its embassy was destroyed and the ambassador hospitalised. Spain said its embassy was badly damaged.

"Haiti has moved to centre of the world's thoughts and the world's compassion," British Prime Minister Gordon Brown said.

Tens of thousands of people lost their homes as buildings that were flimsy and dangerous even under normal conditions collapsed in the shaking. Nobody offered an estimate of the dead, but the numbers were clearly enormous.

"The hospitals cannot handle all these victims," Dr. Louis-Gerard Gilles, a former senator, said as he helped survivors. "Haiti needs to pray. We all need to pray together."

A young American aid worker was trapped for about 10 hours under the rubble of her mission house before she was rescued by her husband, who told CBS's "The Early Show" that he drove 160km to Port-au-Prince to find her when he learned of the quake.

Frank Thorp said he dug for more than an hour to free his wife, Jillian, and a co-worker, from under about a foot of concrete.

Even relatively wealthy neighborhoods were devastated.

An Associated Press videographer saw a wrecked hospital where people screamed for help in Petionville, a hillside district that is home to many diplomats and wealthy Haitians as well as the poor.

At a destroyed four-storey apartment building, a girl of about 16 stood atop a car, trying to peer inside while several men pulled at a foot sticking from rubble. She said her family was inside.

"A school near here collapsed totally," Petionville resident Ken Michel said after surveying the damage. "We don't know if there were any children inside." He said many seemingly sturdy homes nearby were split apart.

The UN's 9000 peacekeepers in Haiti, many of whom are from Brazil, were distracted from aid efforts by their own tragedy: Many spent the night hunting for survivors in the ruins of their headquarters.

"It would appear that everyone who was in the building, including my friend Hedi Annabi, the United Nations' Secretary General's special envoy, and everyone with him and around him, are dead," French Foreign Minister Bernard Kouchner said on RTL radio.

UN peacekeeping chief Alain Le Roy would not confirm that Annabi was dead but said he was among more than 100 people missing in the rubble of its headquarters. He said only about 10 people had been pulled out, many of them badly injured. Fewer than five bodies had been pulled from the rubble, he said.

Brazil's army said at least four of its peacekeepers were killed and five injured, while Jordan's official news agency said three of its peacekeepers were killed and 33 injured. A state newspaper in China said eight Chinese peacekeepers were known dead and 10 were missing - though officials later said the information was not confirmed.

Much of the National Palace pancaked on itself, but Haiti's ambassador to Mexico, Robert Manuel, said President Rene Preval and his wife survived the earthquake. He had no details.

The quake struck at 4:53 pm local time, centred about 15km west of Port-au-Prince at a depth of only 8km, the US Geological Survey said. USGS geophysicist Kristin Marano called it the strongest earthquake since 1770 in what is now Haiti.

Most Haitians are desperately poor, and after years of political instability the country has no real construction standards. In November 2008, following the collapse of a school in Petionville, the mayor of Port-au-Prince estimated about 60 percent of buildings were shoddily built and unsafe in normal circumstances.

Yesterday's quake was felt in the Dominican Republic, which shares the island of Hispaniola with Haiti, and in eastern Cuba, but no major damage was reported in either place.

With electricity knocked out in many places and phone service erratic, it was nearly impossible for Haitian or foreign officials to get full details of the devastation.

"Everybody is just totally, totally freaked out and shaken," said Henry Bahn, a US Department of Agriculture official visiting Port-au-Prince. "The sky is just gray with dust."

President Barack Obama offered prayers for the people of Haiti and said the US stood ready to help. Rajiv Shah, administrator of the US Agency for International Development, said a disaster response team would fly in today.

Edwidge Danticat, an award-winning Haitian-American author was unable to contact relatives in Haiti. She sat with family and friends at her home in Miami, looking for news on the internet and watching TV news reports.

"You want to go there, but you just have to wait," she said. "Life is already so fragile in Haiti, and to have this on such a massive scale, it's unimaginable how the country will be able to recover from this."

NZ FAMILY IN COLLAPSED HOTEL

Kiwi woman Emily Rejouis, desperately searching for her family in earthquake-devastated Haiti, has managed to get her youngest daughter, Alyahna, out of the rubble alive.

It is understood the daughter, 2, was found under the body of her father Emmanuel, and has a broken leg, Radio New Zealand is reporting.

Her husband Emmanuel is believed to be dead while her two other daughters, Zenzie and Kofie-Jade are still  buried under toppled buildings after an earthquake struck the capital of the impoverished Caribbean country yesterday.

Emily Rejouis, originally from Nelson, rang her step-sister Caroline Larnach in Auckland last night on a borrowed satellite phone amid the chaos in Haiti because there were no emergency services on the ground.

An emotional Ms Larnach said the family was desperate to get help to find her step-sister's family.

"We're just absolutely desperate to have some help for our family. We're just absolutely distraught with what's happening.

"We need support from the New Zealand Government and from any services that are represented in Haiti."

Ms Rejouis had returned from the collapsed United Nations building to the Karibe Hotel in Port-au-Prince, to find it a pile of rubble.

Nine Australians known to be in Haiti are safe, but fears remain for others.

Australian aid worker Ian Rodgers says the earthquake struck with "extreme force and ferocity".

"What's resulted is a lot of landsliding, and buildings have collapsed and then fallen down the hillside," he told Network Ten from Port-au-Prince.

"Electricity is now off. We have had reports hospitals are damaged and destroyed. We're trying to find out what is functioning and what is not functioning."

Mr Rodgers - Save the Children's senior emergency adviser - said he could hear people pleading for help.

"There's a lot of distress and wailing of people trying to find loved ones who are trapped under buildings and rubble."

- with MICHAEL FOX, Stuff.co.nz, Reuters, AAP, NZPA