The fiercest storm to hit the region for almost a decade is barrelling its way towards the United States.
More than a million people have been ordered to evacuate the east coast of the US as Hurricane Matthew barrels through the Caribbean bringing 145mph winds.
The fiercest storm to hit the region in almost a decade has brought torrential rain across Haiti and the Dominican Republic.
At least five people have died so far by collapsing walls and mudslides.
The damage in Haiti has been described as "catastrophic", six years after an earthquake killed 200,000 people.
A two-metre high storm surge is expected to sweep coastal towns in Florida, North Carolina and South Carolina in the coming days.
Nikki Haley, the Governor of South Carolina, pleaded with people to get 100 miles away from the coast, but did not say if there would be penalties for those who refuse to comply.
“We don’t do voluntary or mandatory anymore. An evacuation is an evacuation,” Haley said.
Pentagon spokesman Peter Cook said the U.S. Navy was looking at sending an aircraft carrier, the USS George Washington, and other ships to the region to aid relief efforts.
The United States has already offered Haiti the use of some helicopters, said Haitian Interior Minister Francois Anick Joseph.
The minister said roads to the south were blocked, phones were down and the weather meant overflights were impossible.
"It is too early to do a real assessment, but it has been very serious," Anick Joseph added.
The eye of the violent Category 4 Hurricane Matthew passed over Haiti's western tip early on Tuesday, the U.S. National Hurricane Center said, bringing devastating winds, heavy rains and a storm surge with massive waves.
It was forecast to remain extremely powerful as it made its way to Cuba and the Bahamas and a hurricane watch was issued for parts of southeast Florida, which the forecasters said Matthew could reach late on Thursday.
U.S. President Barack Obama canceled a trip to Florida scheduled for Wednesday because of the potential impact of Matthew, the White House said.
Haitian port town Les Cayes, named for the sandy islands off its shore and twice destroyed by hurricanes in the 18th century, was hard hit.
"The situation in Les Cayes is catastrophic, the city isflooded, you have trees lying in different places and you can barely move around, the wind has damaged many houses and taken away their rooftops," said Deputy Mayor Marie Claudette Regis Delerme, speaking from the town of about 70,000 people.
The hurricane comes at a time when tens of thousands of people are still living in flimsy tents and makeshift dwellings in Haiti after a 2010 earthquake that killed more than 200,000 people.
The centre of Matthew was 55 miles south of the eastern tip of Cuba at 4pm GMT.
It was moving north at about 10 miles per hour, the hurricane centre said.
The storm is expected to hit Guantanamo in the far southeast of Cuba later on Tuesday, passing close to the controversial US Naval base and military prison.
The US Navy ordered the evacuation of 700 spouses and children of service personnel as the storm approached.
Florida, South Carolina and Georgia have all declared a state of emergency, meaning resources for evacuations and shelters are being prepared and the National Guard is on standby.
South Carolina Governor Nikki Haley ordered an evacuation of more than a million people in coastal areas.