An overnight curfew was declared by the mayor of New Orleans as Hurricane Isaac brought flooding and high winds to the exposed city.

Isaac weakened to a tropical storm overnight as it moved west of New Orleans.

The storm could take most of the day to travel as far as Baton Rouge, 70 miles to the north west.

Louisiana Governor Bobby Jindal said that the state would be dealing with Isaac “through early Friday morning”.

The BBC reported serious flooding and people stranded by rising waters in the Braithwaite area, just across the Mississippi river from metropolitan New Orleans.

The US National Hurricane Centre warned that the rain threat from Isaac will spread inland over the next few days.

Isaac was downgraded from a hurricane to a tropical storm on yesterday afternoon.

The port of New Orleans has been shut for three days after affecting cruise ship departures from Tampa, Miami and Fort Lauderdale.