"Monster" Hurricane Matthew, the most powerful Caribbean storm in a decade, killed more than 800 people and left tens of thousands homeless in Haiti before it churned northwards off Georgia and South Carolina in southeast US early on Saturday, but spared Florida a direct hit.
The storm, which has been downgraded to Category Two, has caused flooding, wind damage and power failures in North Florida.
Matthew, with winds of 105 miles per hour, is expected to move to North Carolina by night. The storm surges are likely to reach six to nine feet above high tide from Jacksonville, Florida, up through Charleston, South Carolina, reports said.
Haiti has borne the brunt of the storm with nearly 30,000 homes destroyed and 150 lives lost in just one part of the country's southern peninsula.
In many areas, the sugar, banana and mango crops were flattened.
Rescue efforts were hit by the massive destruction all around, with trees and buildings felled and floodwater marooning remote areas.
The UN has warned that it could take days for the full impact of Matthew in Haiti to emerge.
Haiti's Civil Protection Agency on Friday doubled the death toll from the hurricane from 400 to more than 800.
World Food Programme's Haiti Director Carlos Veloso said some of the hard-hit towns in Haiti can be accessed only by air or sea.
Matthew battered Haiti's western peninsula on Tuesday with 145 miles per hour (233 km per hour) winds and torrential rain. More than 61,500 people are in shelters, officials said,
Mobile phone networks are down and roads flooded, making it difficult for aid to reach hard-hit areas in Haiti.
The Mesa Verde, a US Navy amphibious transport dock ship, was headed for Haiti to support relief efforts. The ship has heavy-lift helicopters, bulldozers, fresh water delivery vehicles and two surgical operating rooms.
At least one major town in the south - Jeremie - has been 80 per cent destroyed, with aerial footage showing the scale of destruction with hundreds of flattened houses.
The storm passed directly through the Tiburon peninsula - encompassing Haiti's entire southern coast - driving the sea inland and flattening homes with winds of up to 230km/h and torrential rain, BBC reported.
The Red Cross has launched an emergency appeal for $6.9m, "to provide medical, shelter, water and sanitation assistance to 50,000 people".
There have been concerns over a surge in cholera cases, with at least seven deaths reported.
A 2010 earthquake in Haiti killed thousands of people.
After slicing through Haiti and Cuba, Matthew pounded the Bahamas on Thursday but no fatalities were reported there.
Four people died in the neighbouring Dominican Republic on Tuesday.
As it approached Florida, the storm swept past the coast with winds of up to 120 mph (195 kph) but did not make landfall in the state.
The US National Hurricane Center (NHC) downgraded the storm to Category 2 on the five-step Saffir-Simpson scale as its sustained winds dropped to 110 mph. Category 5 is the strongest.
Four storm-related deaths were reported in Florida but no immediate reports of significant damage in cities and towns where waves swept through streets, toppled trees and knocked out power to more than 1 million people, the Telegraph reported.
More than two million people had been ordered to evacuate the area.
US President Barack Obama on Friday warned that, while southern Florida had been spared the worst, the hurricane remained very dangerous, and the risk of a storm surge and flooding remained real.
A state of emergency is in place in several states of US.