A strong earthquake with a magnitude of 7 on the Richter scale struck Tuesday near Haiti's capital Port-au-Prince, blocking roads, collapsing buildings and leaving bodies strewn in the streets, dpa reported.
The quake struck at 2153 GMT Tuesday, some 15 kilometres south- west of the capital Port-au-Prince at a depth of 10 kilometres.
Two aftershocks registering 5.9 and 5.5 on the Richter scale followed within the hour, with more temblors later.
A CNN producer who was born in Haiti said she had talked to a family member and a friend in Haiti, both of whom described bodies in the streets.
Raymond Alcide Joseph, Haitian ambassador to the United States, told CNN that he had managed to reach only one government official in Haiti after hours of frantic calling. The official described a "catastrophe of major proportions."
The official told him the quake occurred as he was driving home, and he had to stop. He was trying to reach his home on foot and was walking past "houses that were crumbling" on both sides of the road. He would have to cross a bridge to get home and had no idea if the bridge was still standing.
Ian Rogers, a Save the Children worker in Haiti, told CNN that all roads were blocked and the only vehicles capable of moving around were motorcycles. He said roads were "slipping off the sides of mountains."
"It's dark, and people are trapped. People are in a great deal of distress," he told CNN.
The quake triggered a small tsunami of about 12 centimetres, which washed across Santo Domingo in Dominican Republic, which shares the island of Hispanola with Haiti, according to the Pacific Tsunami Warning Centre.
A tsunami warning was still in effect for Puerto Rico and the Virgin Islands but was cancelled for the rest of the region including Haiti, Cuba, the Bahamas and the Dominican Republic.
Frank Williams, an aide worker with World Vision, told CNN that buildings were damaged across Port-au-Prince, and walls had collapsed into the streets, blocking traffic.
With a population of 9 million, Haiti is the poorest country in the western hemisphere and has been marred by political turmoil for decades. The United Nations extended its 7,000-member mission in the impoverished country late last year.
In Washington, US President Barack Obama immediately offered help.
"My thoughts and prayers go out to those who have been affected by this earthquake," Obama said in a statement. "We are closely monitoring the situation, and we stand ready to assist the people of Haiti."
Obama asked his staff to begin preparations for humanitarian assistance if it is needed.
The Department of State, the US Agency for International Development and the US military's Southern Command have begun working to coordinate an assessment for assistance, the statement said.
The extent of casualties and damage were not immediately clear.