A magnitude-7.0 earthquake has hit the impoverished Caribbean nation of Haiti, causing major damage in the capital of Port-au-Prince -- home to about two million people.

Pictures of the devastation were uploaded to Twitter and other networking sites Tuesday, showing bodies amid the rubble and wounded survivors lying on the ground. Thousands are feared dead.

The headquarters of the UN Peacekeeping Mission in Haiti sustained "serious damage" and a large number of UN personnel are unaccounted for.

A Department of National Defence spokesperson said five Canadians are attached to the UN mission in Haiti and there has not been any communication from them yet.

Another 56 Canadians, all members of an Ontario church, were reported to be safe late Tuesday. They had travelled to Haiti on a humanitarian mission.

Henry Bahn, an official with the U.S. Department of Agriculture who is visiting the country, said the quake made the sky "grey with dust."

"Everybody is just totally, totally freaked out and shaken," said Bahn, who was walking to his hotel room when the quake struck. "I just held on and bounced across the wall."

The temblor reportedly destroyed a hospital, damaged the presidential palace and sent a widespread cloud of dust into the air, leading to suggestions that many concrete buildings may have collapsed across the city. One U.S. government official said he saw houses that had fallen into a ravine.

The U.S. Geological Survey said the quake was centred 15 kilometres southwest of the capital. It struck at 4:53 p.m. EST and originated about 8 kilometres below ground, the agency said. Anywhere between five and 13 aftershocks followed, with one as powerful as 5.9.

USGS geophysicist Kristin Marano called it the strongest earthquake to hit the area in more than two centuries.

Raymond Joseph, Haiti's ambassador to the U.S., told CNN the quake represented "a major catastrophe."

Joseph said he spoke to President Rene Preval's chief of staff, Fritz Longchamp, immediately after the quake. Longchamp told him that "buildings were crumbling right and left" near the national palace, Joseph said.

But reports on the extent of the casualties and damage were sporadic, as the city's power grid and phone lines were apparently knocked out.

Minister of Foreign Affairs Lawrence Cannon estimated there may be as many as 6,000 Canadians in the country, and said that Ottawa is monitoring the situation "very closely."

"Our thoughts are with the people of Haiti, and with Canadians of Haitian descent who are worried about their loved ones," Cannon said at a press conference Tuesday evening. "It's a country that receives lots of help from Canada, lots of aid, and in a period of distress it's not time to abandon our friends."

Haiti is the second-largest recipient of Canadian aid, behind Afghanistan.

Cannon added that the Canadian embassy was being evacuated as a precautionary measure. He advised Canadians in Haiti to seek consular assistance by phone.

  • Canadians concerned about relatives in Haiti can call the emergency operations centre in Ottawa at 1-800-387-3124.

U.S. President Barack Obama issued a statement about the situation early Tuesday evening.

"My thoughts and prayers go out to those who have been affected by this earthquake. We are closely monitoring the situation and we stand ready to assist the people of Haiti," Obama said.

The White House said the Department of State, USAID and the U.S. Southern Command were "working to co-ordinate an assessment," and assistance.

Don Blakeman, an analyst at the USGS, said Port-au-Prince likely suffered major damage.

A spokesperson for the U.S. State Department, Gordon Duguid, said the American embassy in Port-au-Prince was reporting "just total disaster and chaos" in the city.

Haiti's consul general in New York, Felix Augustin, said he was worried about everyone in the country, including his extended family.

"Communication is absolutely impossible," he said. "I've been trying to call my ministry and I cannot get through.... It's mind-boggling."

Haiti is the least-developed country in the western hemisphere. Most of its 9 million residents live in poverty, and construction standards are weak.

The quake was also felt in the Dominican Republic, which sits on the same island of Hispaniola, and in Cuba.

With files from The Associated Press