Hundreds of people were rescued by boat and helicopter as floodwaters inundated North Carolina towns on Monday in the wake of Hurricane Matthew, and officials warned that life-threatening flooding from swollen rivers would continue for days.

Matthew, the most powerful Atlantic storm since 2007, was downgraded to a post-tropical cyclone on Sunday.

The hurricane killed around 1,000 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."