The number of deaths in Haiti, the poorest country in the Americas, surged to at least 877 on Friday as information trickled in from remote areas previously cut off by the storm, according to a Reuters tally of death tolls given by officials.
Matthew triggered mass evacuations along the U.S. Atlantic coast from Florida northward through Georgia and into South Carolina and North Carolina. President Barack Obama urged people not to be complacent and to heed safety instructions.
"The potential for storm surge, loss of life and severe property damage exists," Obama told reporters after a briefing with emergency management officials about the fiercest cyclone to affect the United States since Superstorm Sandy four years ago.
Matthew smashed through Haiti's western peninsula on Tuesday with 145 mph (233 kph) winds and torrential rain. Some 61,500 people were in shelters, officials said, after the storm hurled the sea into fragile coastal villages, some of which were only now being contacted.
While highlighting the misery of underdevelopment in Haiti, which is still recovering from a devastating 2010 earthquake, the storm looked certain to rekindle debate about global warming and the long-term threat posed by rising sea levels to low-lying cities and towns.
Read alsoHurricane Matthew batters Florida as Haiti death toll rises – ReutersAt least three towns in the hills and coast of Haiti's fertile western tip reported dozens of people killed, including the farming village of Chantal where the mayor said 86 people died, mostly when trees crushed houses. He said 20 others were missing.
With cellphone networks down and roads flooded, aid has been slow to reach hard-hit areas in Haiti. Food was scarce and at least seven people died of cholera, likely because of flood water mixing with sewage.
The Mesa Verde, a U.S. Navy amphibious transport dock ship, was heading for Haiti to support relief efforts. The ship has heavy-lift helicopters, bulldozers, fresh-water delivery vehicles and two surgical operating rooms.