|Witnesses reported that many buildings had collapsed in the quake [AFP]
The Caribbean nation of Haiti has been hit by its strongest earthquake in more than 200 years, causing what is being described as "a catastrophe of major proportions".
Centred about 15km inland, west of the capital Port-au-Prince, Tuesday afternoon's quake caused buildings to collapse and is believed to have left hundreds of people trapped under the rubble.
Joseph Guyler Delva, a reporter with the Reuters news agency, said he saw dozens of casualties.
"Everything started shaking, people were screaming, houses started collapsing," he said. "It's total chaos."
As darkness fell in Port-au-Prince, residents desperately tried to dig out survivors or searched for missing relatives in debris-strewn streets amid chaotic scenes.
'City in darkness'
A Food for the Poor charity employee said there that there were likely to be many casualties given the destruction he had witnessed in the capital.
"The whole city is in darkness, you have thousands of people sitting in the streets, with nowhere to go," Rachmani Domersant, the charity's operations manager, said.
"I've seen seven to eight buildings, from office buildings to hotels and shopping stores, collapsed ... I think hundreds of casualties would be a serious understatement."
Karel Zelenka, a Catholic Relief Services representative in Port-au-Prince, told colleagues in the US that "there must be thousands of people dead", according to a spokeswoman for the aid group.
Sara Fajardo said from Catholic Relief's offices in Maryland: "[Zelenka] reported that it was just total disaster and chaos, that there were clouds of dust surrounding Port-au-Prince."
The presidential palace in the capital was among the buildings badly damaged, Raymond Alcide Joseph, Haiti's ambassador to the US, said.
Joseph told Al Jazeera that he had spoken to Fritz Longchamp, chief of staff to Haiti's president, who said "buildings were crumbling right and left" near the palace.
"I think it's really a catastrophe of major proportions," Joseph said.
The Caribbean nation of nine million is the poorest country in the Americas with an annual per-capita income of $560. It ranks 146th out of 177 countries on the UNDP Human Development Index
More than half the population lives on less than $1 a day and 78 per cent on less than $2. There is a high infant mortality rate and the prevalence of HIV among those between ages 15 and 49 is 2.2 per cent
Haiti's infrastructure is close to total collapse and severe deforestation has left only two per cent of forest cover
About 9,000 UN police and troops are stationed in the country to maintain order
Rene Preval, the president, and his wife were both reported to be alive.
Hospitals, schools and hotels collapsed in the capital, raising fears that the injured would have nowhere to go to get treatment.
"We have reports of some of the most important hospitals in Port-au-Prince have been severely impacted by the earthquake," Paul Conneally, the Head of Media at the International Federation of Red Cross and Red Crescent Societies, told Al Jazeera.
"Other hospitals are operational, but are turning people away because they are compeltely overwhelmed."
Alain Joyandet, the French secretary of state for co-operation, told the AFP news agency that up to 200 people were missing after the Hotel Montana was levelled.
"We know there were 300 people inside the hotel when it collapsed, only around 100 have got out, which greatly concerns us," he said.
Television footage showed long cracks in many of the buildings that were still standing.
The United Nations headquarters in the capital was also reported to be severely damaged and many of its staff were missing.
"The United Nations can confirm that the Headquarters of the United Nations Stabilisation Mission in Haiti (Mintusah) in Port-au-Prince has sustained serious damage along with other UN installations," Alain le Roy, the under-secretary-general for peacekeeping operations, said in a statement issued in New York.
"For the moment, a large number of personnel remain unaccounted for."
The magnitude 7.0 quake's epicentre was about eight to 10km deep, a relatively shallow depth which was likely to have magnified the destruction, according to seismologists.
The quake, which was followed by at least 27 aftershocks up to 5.9 in magnitude, prompted a tsunami alert for parts of the Caribbean that was later cancelled.
Patrick McCormick, a spokesman for Unicef, told Al Jazeera that the quake had created a "massive emergency" and the UN children's agency was "looking at bringing supplies especially water, medicine and shelter to those affected".
Thoughts and prayers
Barack Obama, the US president, said his thoughts and prayers were with the people of Haiti and the US was ready to help the island nation.
Hillary Clinton, Obama's secretary of state, said the US would provide civilian and military disaster relief assistance.
Tuesday's quake was felt as far away as southeastern Cuba, about 257km from the epicentre, prompting Cuban authorities to evacuate coastal residents because of the initial tsunami threat.
Soldiers at the US naval base at Guantanamo Bay in eastern Cuba also felt the quake but there was no damage to the base or the prison where the US holds about 200 foreign detainees.
|Many people are feared buried under the rubble of buildings that fell in the quake [AFP]
Chief Petty Officer Bill Mesta, a sailor at the base, said troops had begun checking stockpiles of blankets, tents and other relief supplies in anticipation that they will be asked to help in the relief effort.
The last major earthquake that hit Haiti - a magnitude 6.7 quake – struck in 1984.
Already the poorest nation in the Americas, Haiti has been hit by a series of disasters recently and was battered by hurricanes in 2008.
Michael Zamba of the Pan American Development Foundation said that the disaster would be a "tremendous setback" for Haiti.
"A year ago Haiti was hit by four back-to-back tropical storms and hurricanes. That wiped about 20 per cent off the Gross Domestic Product," he told Al Jazeera from Washington DC.
"It has not yet recovered from that last series of natural disasters and this only compounds the situation.
"Haiti is a food insecure nation, it is a nation that needs a lot of food assistance, this is only going to push it back further."