Haitian politicians fear over 100,000 people could be dead, as citizens pile bodies along the devastated streets of the capital city of Port-au-Prince.

The chaos comes after a powerful earthquake flattened the president's palace and the main prison, the cathedral, hospitals, schools and thousands of homes. Untold numbers are still trapped.

President Rene Preval says he believes thousands of people are dead even as other officials give much higher estimates -- though they were based on the extent of the destruction rather than firm counts of the dead.

His prime minister, Jean-Max Bellerive, tells CNN: "I believe we are well over 100,000," while leading senator Youri Latortue tells The Associated Press that 500,000 could be dead. Both admit they have no way of knowing.

The magnitude-7 quake struck Tuesday afternoon.

The U.N. says more than 100 people are missing in the rubble of the collapsed U.N. headquarters building in Haiti, including the mission chief.

Canadians dead, missing

Nurse Yvonne Martin, from Elmira, Ont. was among a group of seven nurses who arrived in the Haitian capital Port-au-Prince around 4:30 Tuesday afternoon.

The nurses, who are all from southern Ontario, arrived about 90 minutes before the earthquake hit, Lou Geense, of the Emmanuel Missionary Church of Canada, told CTV's Michael Melling.

Meanwhile, former Liberal MP Serge Marcil is missing after also arriving in the Haitian capital Tuesday afternoon.

Marcil, who currently works for Montreal engineering firm SM International, was booked to stay at the Montana Hotel, which reportedly collapsed during the quake.

An official with SM International could not confirm Wednesday afternoon if Marcil had checked into the hotel.

Millions affected

International Red Cross spokesman Paul Conneally said an estimated three million people may have been affected by the quake and that it would take a day or two for a clear picture of the damage to emerge.

Aftershocks rattled the city of two million people as women covered in dust clawed out of debris, wailing. Stunned people wandered the streets holding hands. Thousands gathered in public squares singing hymns.

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

International aid efforts

Canada will send $5 million in immediate aid to Haiti in addition to the full weight of its disaster assistance capabilities, Canadian officials announced Wednesday afternoon.

Foreign Affairs Minister Lawrence Cannon said the $5 million is an initial contribution by Canada for urgent humanitarian assistance and gathering supplies that will be badly needed in the Western Hemisphere's poorest country.

"This will help provide emergency shelter, medical service, food, relief items, water and sanitation services, as well as offer protection," Cannon told reporters after cabinet ministers met with Prime Minister Stephen Harper in Ottawa.

"Canada continues to work closely with local authorities, international organizations and UN agencies to help bring relief to those affected and provide support."

He said the team's assessment will provide guidance for the deployment of Canada's Disaster Assistance Relief Team, or DART, a military quick-reaction force for humanitarian aid.

Foreign Affairs has opened phone lines for Canadians who need information from Haiti.

That number is 1-800-387-3124.

Canadians affected

There are 707 Canadians registered with the Canadian Embassy in Haiti, but some 6,000 Canadians are believed in the Caribbean country. Among them are 83 Canadian police officers, seven corrections officials and five Canadian Forces personnel.

The Red Cross and other aid groups also announced plans for major relief operations.

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

It was clear tens of thousands lost their homes and many perished in collapsed buildings that were flimsy and dangerous even under normal conditions.

"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."

Survival stories

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 160 kilometres 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 neighbourhoods 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 Wednesday after surveying the damage. "We don't know if there were any children inside." He said many seemingly sturdy homes nearby were split apart.

UN devastated

UN peacekeepers, 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 Wednesday, speaking on RTL radio.

At least four Brazilian soldiers were killed and five injured, Brazil's army said. Jordan's official news agency said three of its peacekeepers were killed and 21 were 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.

Some 9,000 peacekeepers have been in Haiti since 2004, including 1,266 Brazilians.

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.

Struck in late afternoon

The quake struck at 4:53 p.m., centred 15 kilometres west of Port-au-Prince at a depth of only eight kilometres, the U.S. Geological Survey said. USGS geophysicist Kristin Marano called it the strongest earthquake since 1770 in what is now Haiti.

Most of Haiti's nine million people 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 per cent of buildings were shoddily built and unsafe in normal circumstances.

Tuesday'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 telephone 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 U.S. Department of Agriculture official visiting Port-au-Prince. "The sky is just grey with dust."

In Washington, State Department spokesman P.J. Crowley said that U.S. Embassy personnel were "literally in the dark" after power failed.

"They reported structures down. They reported a lot of walls down. They did see a number of bodies in the street and on the sidewalk that had been hit by debris. So clearly, there's going to be serious loss of life in this," he said.

On Haiti

Haiti is the poorest country in the Western Hemisphere. It gained independence from France in 1804, and since then, the country has struggled with political upheaval, military rule and abject poverty.

Haiti has also been hard-hit by several natural disasters in recent years, including four hurricanes and strorms in 2008 that left hundreds dead.

Today, just over 9 million people live in Haiti, almost half of which live in cities.

Eighty per cent of Haitians live below the poverty line, and the average citizen makes about $560 a year.

- With files from The Canadian Press -