Thousands of people in the US have fled their homes as Hurricane Gustav moves within 24 hours of striking.

There were mass evacuations in New Orleans and the Gulf Coast, while the US oil industry from Texas to Louisiana shut down nearly all offshore platforms and many refineries.

New Orleans Mayor Ray Nagin ordered mandatory evacuation of the city of 239,000 and told residents: "This is still a big, ugly storm, still strong and I encourage everyone to leave."

The storm evoked memories of Katrina which struck almost exactly three years ago, flooding 80 percent of the city and killing 1,500 people.

Gustav also took centre stage in US politics two months ahead of the hotly contested presidential election.

President George W Bush and Vice President Dick Cheney said they would not attend this week's Republican National Convention in St. Paul, Minnesota. Mr Bush will travel to Texas on Monday to oversee emergency efforts.

Republican presidential nominee John McCain headed to the Gulf to survey preparations and ordered most of the party's convention's activities be suspended on Monday, the first day of the gathering.

The US Coast Guard reported the first storm-related death in Florida, where a man fell overboard as his ship ran into heavy waves.

If Gustav lands west of New Orleans on Monday as a Category 4 hurricane with wind speeds up to 155mph, a 16ft storm surge could break through the same levees that failed three year ago.

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