A weakened Hurricane Matthew made landfall Saturday in South Carolina, nearing the end of a four-day rampage that left a trail of death and destruction across the Caribbean and up the southeastern US coast, now swamped by record floods.

In Haiti, where Matthew was a monster Category 4 when it slammed into the poorest country in the western hemisphere Tuesday, the official death toll rose to at least 336.

Nine were killed in the United States.

The interim president of Haiti, Jocelerme Privert, announced three days of national mourning, beginning Sunday.

The scope of the devastation in the south of the Caribbean country was becoming clearer but the toll remains provisional due to the difficulty of gaining access to some areas.

At least 336 people were dead, the head of Haiti's civil protection services, Marie-Alta Jean Baptiste, told AFP. "We won't have a definitive toll before Wednesday," she said.

Other officials said earlier that at least 400 were dead.

Half a million children live in the worst-hit departments in southern Haiti, according to UNICEF, which said it needed at least $5 million to meet their immediate needs.

Pledges of aid have flooded in, with the United States announcing it was sending the USS Mesa Verde, whose 300 Marines will add to the 250 personnel and nine helicopters already ordered to deploy to Haiti.

France announced it was sending 60 troops, with 32 tonnes of humanitarian supplies and water purification equipment.

California-based charity International Relief Teams said it was donating $7 million in medical supplies with international organizations MAP International and Hope for Haiti.

- US toll rises -

Matthew, downgraded to the lowest-level Category 1 hurricane, lashed the coast of South Carolina as the storm moved inland. It then approached coastal North Carolina on Sunday, with record flooding expected.

Despite flooding, fallen trees and power outages, most of the American southeast appeared to have been spared catastrophic damage as the storm surge turned out to be less severe than expected.

At 0600 GMT, Matthew was just 30 miles (50 kilometers) south southwest of Cape Hatteras, North Carolina.

"Matthew should move near or just south of the coast of North Carolina this morning and east of the North Carolina coast by this afternoon," the National Hurricane Center (NHC) in Miami forecast.

As Matthew approached -- after storming through Haiti, the Dominican Republic, Jamaica, Cuba and the Bahamas -- millions of Americans were ordered to evacuate and curfews were slapped on cities.

On Saturday, the center of Matthew made landfall in the South Carolina town of McClellanville and there was a "serious inland flooding event unfolding," the NHC said.

It also warned that storm-churned swells from Matthew would "likely cause life-threatening surf and rip current conditions".

McClellanville is about 35 miles (56 kilometers) northeast of Charleston, a port city with a historic city center.

The hurricane had maximum sustained winds of a still-dangerous 75 miles (120 kilometers) per hour.

The NHC also predicted hurricane and tropical storm conditions in Georgia and South Carolina that could produce "life-threatening" flooding.

President Barack Obama declared federal states of emergency in Florida, Georgia, and North and South Carolina.

At least four people died in Georgia -- including at least three killed by falling trees, officials said. Five people died in hurricane-related incidents in Florida.

- St Augustine damage -

The mayor of Georgia's ocean-fronting community of Tybee Island described Matthew as the worst storm to hit the area since 1898.

Nearly 120,000 customers remained without power in the city of Savannah and its surrounding Chatham County, officials said.

Various roads were still impassable, there was a curfew on Savannah for a second night running and residents became increasingly frustrated that they were prevented from returning to homes.

Eric Thomas, 42, a local business owner, brought his own chainsaw to cut down a fallen tree that blocked access on the road from Savannah to Tybee Island, desperate to get home.

Although he and his friends cleared the road, police barred residents from driving across until Sunday at the earliest.

Thomas told AFP that he heard there was "substantial" damage on the island.

"We're concerned for their safety. I've been riding this entire county, and it's scary," Chatham County Chairman Al Scott told reporters.

In Florida, power was slowly being restored. Officials said that some 879,000 customers -- or nine percent -- were still without electricity.

In Jacksonville, Florida, the rain had stopped. There were fallen trees and flooding but no major damage.

But the nearby historic town of St Augustine, a former Spanish settlement that calls itself the nation's oldest city, was not so lucky.

There was "a lot of damage," Commander Chuck Mulligan, spokesman for the St Johns County Sheriff's Office, told AFP.