At least seven people are believed to have been killed after a Category 4 storm struck Haiti and the Dominican Republic early on Tuesday.
Hurricane Matthew made landfall on the western tip of Haiti at 11am GMT, packing winds of up to 145mph (230kmh), and lashing coastal communities with rain and sea swells.
"It's much too early to know how bad things are but we do know there are a lot of houses that have been destroyed or damaged in the south," Marie Alta Jean-Baptiste, the director of the country's civil protection agency, told the Associated Press.
Prospery Raymond, country manager for the international charity Christian Aid, said three to five people had been reported dead in Haiti and three children were thought to have been killed in the Dominican Republic.
One man died when a wave crashed through his home in the beach town of Port Salut, Haiti's civil protection service said. He had been too ill to leave for a shelter, according to officials. A fisherman was also reported missing.
Associated Press reported at least seven confirmed deaths.
Haiti's Interim President Jocelerme Privert said earlier that some people at sea or who had not "respected alerts" had died, but gave no more details.
River levels in Haitian capital Port au Prince have also risen to dangerous levels after days of heavy rainfall.
Authorities had attempted to evacuate people from their homes in vulnerable coastal areas, but people were reportedly reluctant to leave their homes, fearing their belongings would be looted.
Thousands of people in Haiti still live in tents and other temporary shelters after the devastating earthquake that struck the island in 2010.
Haitian officials say that about 1,300 emergency shelters have been built, enough to accommodate 340,000 people. Both airports in Haiti are closed.
The storm will move over lightly populated eastern parts of Cuba late on Tuesday and early Wednesday. A hurricane warning has been issued by authorities for the south Florida area.