New Orleans residents have been fleeing in their thousands after the city’s mayor ordered an evacuation ahead of Hurricane Gustav’s expected landfall.

Roads out of the Louisiana port have been crammed with traffic and authorities have been helping those unable to leave by their own means.

Gustav, set to hit the US Gulf Coast on Monday, was described by Mayor Ray Nagin as “the storm of the century”.

It comes three years after Hurricane Katrina devastated New Orleans.

In 2005, three-quarters of the city was flooded after a storm surge breached its protective levees. More than 1,800 people died in coastal areas.

Gustav, which is forecast to strengthen to a Category 5 storm over the Gulf, powered through western Cuba overnight.

At least 300,000 people were evacuated in Cuba as the storm brought extensive flooding and some severe damage, but no reports of fatalities.

The storm, which has now moved into the Gulf of Mexico, currently has maximum sustained winds of nearly 240km/h (150mph), with even stronger gusts.

The BBC’s Kevin Connolly, in New Orleans, says Mr Nagin spoke in “passionate and desperate” terms, telling a televised news conference the storm was “so powerful” and growing more powerful every day.

“I’m not sure we’ve seen anything like it,” he told reporters at City Hall.

He warned that in the West Bank area of New Orleans, the highest levees were just eight to 10 feet, and were at risk from storm surges that could be as high as 24 feet.

The floodwalls of the Harvey Canal – a waterway designed to protect residents from surges in Lake Pontchartrain – were not yet completed, the mayor said, warning that water would “punch through holes” and flood nearby areas.

“If you are stubborn enough, if you are not taking this as seriously as we need you to take it, and if you decide to stay; you are on your own,” he said.

“Anyone who decides to stay, I’ll say it like I said it before Katrina: make sure you have an axe, because you will be carving your way, or busting your way out of your attic to get on your roof with waters that you will be surrounded with in this event.”

‘We’re feeling very insecure’

Hundreds of thousands of people are already thought to have obeyed the mayor’s order to flee, clogging roadways, emptying petrol stations of fuel and jamming phone networks.

At the city’s main transit terminal, reports said a line snaked for more than a mile as residents with no other means of getting out waited to board buses bound for shelters in north Louisiana and beyond.

Louisiana Governor Bobby Jindal, in New Orleans to observe the evacuation taking place, said about 700 people an hour could be flown out of the city.

Sarah Debacher, who has lived in New Orleans for 10 years and is preparing to leave her home for the fourth time, told the BBC she was feeling more anxious this time round.

“The failure of the federal levees after Hurricane Katrina meant that we experienced devastation that we shouldn’t have experienced.

“We don’t know, frankly we don’t have a lot of faith in the work that’s been done to repair the damage that was caused by those failures and by the storm. So, this time we’re feeling very insecure.”

City, state and federal officials will be mindful that the reaction to Gustav will be closely scrutinised, not least because the slow and uncoordinated response to Hurricane Katrina was blamed for exacerbating the 2005 disaster.
Eric Blake, from the US National Hurricane Centre in Florida, told the BBC Mr Nagin may have over-stated the size of the hurricane.

“I think that may be a bit of an exaggeration. I mean, they already had Hurricane Katrina, and right now this is no Hurricane Katrina. But we still think it will be a large and powerful hurricane and a significant threat.”

Republican convention doubts

Hours before Mr Nagin spoke, a hurricane watch was put in place along America’s North Gulf coast, from Texas along to the Alabama-Florida border.

Republican party presidential candidate John McCain and his running mate Sarah Palin were travelling to Mississippi on Sunday to observe storm preparations.

Republican officials are considering what to do about the party’s National Convention (due to open on Monday) depending on when and where the storm hits.

Mr McCain hinted there might be changes to the tone of the gathering, rather than a cancellation of the event.

He told Fox News: “You know it just wouldn’t be appropriate to have a festive occasion while a near tragedy or a terrible challenge is presented in the form of a natural disaster, so we’re monitoring it from day to day and I’m saying a few prayers, too.”

The hurricane has already claimed the lives of more than 80 people in the Caribbean.

It has swept through Haiti, the Dominican Republic and Jamaica over the past week, causing widespread damage.

It has strengthened rapidly from a tropical storm to a Category 4 hurricane, and is expected to grow to a Category 5 storm – the maximum on the scale – as it crosses the Gulf of Mexico.

Source: BBC