Scientists with the U.S. Geological Survey say the earthquake struck about 10 kilometers from Port-au-Prince, Tuesday afternoon. The initial quake registered at magnitude 7 on the Richter Scale and was followed by several other shocks, including one that measured 5.9.
Julie Dutton is a geophysicist with the U.S. Geological Survey.
"It is a pretty significant earthquake," Dutton said. "Given the size and location, we are anticipating some significant damage from the region."
Witnesses said a hospital in the capital collapsed, a luxury hotel in Petionville had sustained major damage and many other buildings were destroyed. The United Nations said there was serious damage to the headquarters of its mission in Haiti, and a large number of staff were unaccounted for.
Additional information from the island has been slow in coming, as telephone service from abroad has been disrupted.
Geophysicist Julie Dutton says she expects the damage to be severe, in part because many buildings are not designed to withstand earthquakes.
"This is actually the largest earthquake we have seen in the last 200 years in this region," she noted. "There has not been a earthquake of Magnitude 6 range since the 1970s."
In Washington, President Barack Obama said the country stood ready to assist the people of Haiti and said his thoughts and prayers go out to those affected by the quake.
Secretary of State Hillary Clinton said officials were beginning to assess the disaster and deploy emergency aid to Haiti.
"The United States is offering our full assistance to Haiti and others in the region. We will be offering both civilian and military disaster relief and humanitarian assistance," Clinton said.
Officials with the U.S. Agency for International Development said they were preparing to send a response team that includes 72 people, six search and rescue dogs and 48 tons of rescue equipment.
The quake was also felt in Dominican Republic, which shares the island of Hispaniola with Haiti. Residents on the nearby island of Cuba also said they felt the quake, but no damage was reported.