Hundreds of people have been rescued by boat and helicopter as floodwaters inundated North Carolina in the wake of Hurricane Matthew with officials warning that life-threatening flooding from swollen rivers will continue for days.
Matthew, the most powerful Atlantic storm since 2007, was downgraded to a post-tropical cyclone on Sunday.
The hurricane killed around 1000 people in Haiti and United Nations Secretary-General Ban Ki-moon said on Monday some Haitian towns and villages had just about been "wiped off the map."
In the United States, the number of fatalities rose to at least 23, with nearly half in North Carolina.
After receiving as much as 39cm of rain from Matthew over the weekend, North Carolina's skies were clear on Monday, but raging rivers and breached levees posed major problems.
"This storm is not over in North Carolina," Governor Pat McCrory told reporters in Fayetteville.
"It's going to be a long, tough journey."
Eleven people have died in the state, officials said. With rivers rising, the governor said he expected deaths to increase.
The flooding prompted US President Barack Obama to declare a state of emergency in North Carolina on Monday, making federal funding available to affected individuals in 10 counties hit by the storm, the White House said in a statement.
Some 2000 residents were stuck in their homes and on rooftops in Lumberton, off the Lumber River, after the city suddenly flooded on Monday morning, McCrory said. Air and water rescues would continue throughout the day, he said.
Major flooding was expected this week in central and eastern towns along the Lumber, Cape Fear, Neuse and Tar rivers. The National Weather Service said the Neuse River would crest on Friday night and forecast "disastrous flooding."
Emergency officials in North Carolina's Lenoir County issued a mandatory evacuation order on Monday afternoon for residents and businesses along the Neuse River.
Meanwhile, a federal judge has granted a request from Florida's Democratic Party to extend the state's voter registration deadline by one more day, through Wednesday, because of the hurricane. Republican Governor Rick Scott had rejected demands from Democrats to extend the deadline.
