NEW ORLEANS - HURRICANE Gustav was downgraded Monday to a Category Two storm but remained an 'extremely serious' threat as it neared the Louisiana coast 80 miles (130 kilometres) from New Orleans, the National Hurricane Center said.

'Gustav weakens to a Category Two hurricane (on the 1-5 Saffir-Simpson scale)... eyewall moving onto the southwest Louisiana coast,' the NHC reported in its 1300 GMT advisory, adding that sustained winds decreased slightly to near 110 miles (175 kilometres) per hour.

Earlier, strong winds and rain from Hurricane Gustav lashed the US Gulf coast on Monday, after nearly two million people fled the state of Louisiana ahead of the killer storm.

The exodus is being called the largest evacuation in US history, and officials have also shut down the area's vital oil production facilities.

Reports of power outages in parts of New Orleans trickled in after wind and rain began hitting the city - still struggling to recover from the devastation of Hurricane Katrina, which struck almost exactly three years ago.

'The outer edge of the storm is already over the Mississippi Delta and going in toward New Orleans now, according to radar,' National Hurricane Center meteorologist Patricia Wallace said.

However, the eye of the storm was not expected to make official landfall until early Monday afternoon.

At 0600 GMT, the eye was located 275 kilometres southeast of New Orleans and moving northwest at 16 miles an hour.

However, Gustav has a wide swing, with tropical storm force winds extending as far as 220 miles outward, the center said in its advisory.

Still a category three hurricane, Gustav packed sustained winds of 115 miles per hour.

Forecasters predicted a slight strengthening before landfall, but Gustav was expected to stay at category three for the rest of its journey across the Gulf of Mexico.

'This is a serious storm,' Louisiana Governor Bobby Jindal said Sunday.

People in the state capital of Baton Rouge and other inland areas have been warned to watch for storm-spawned tornados.

Gustav is also wreaking havoc with the US political calendar, forcing US President George W. Bush to cancel plans to appear at the Republican National Convention in St. Paul, Minnesota.

The US leader said Sunday that he would instead travel to Texas to monitor the storm.

Republican presidential hopeful John McCain drastically scaled back the program for the first day of the convention on Monday, saying all activities would be suspended 'except for those absolutely necessary'.

'I hope and pray we will be able to resume some of our normal operations as quickly as possible,' he told reporters via a video link from St. Louis, after returning from a tour of relief preparations in Mississippi.

Military and civilian disaster relief operations were in full swing with the memory of the destruction wrought by Katrina, and the local and federal governments' botched response.

Katrina made landfall near New Orleans on August 29, 2005, smashing poorly-built levees surrounding the city and causing massive floods that destroyed tens of thousands of homes and killed nearly 1,800.

Louisiana officials said there were about 750 National Guard troops already on the ground in New Orleans if needed for rescue operations.

Mayor Ray Nagin on Sunday ordered a sundown curfew in the city and vowed to throw looters into prison.

He told local television that the city had become a 'ghost town' after a massive evacuation campaign, and that only about 10,000 residents remained.

Some of those who left said they felt reassured.

'The mayor assured us our property will be safe,' Mr Wilson Patterson, 48, said as he prepared to board a bus with wheelchair-bound 84-year-old Earline Martin.

'We don't want to get caught up in the Katrina craziness,' he said, recalling the lawlessness that swept New Orleans in 2005.

Jindal said search and rescue teams were already in place.

'We will begin search-and-rescue operations as soon as we safely can. That would be when winds are below 140 miles per hour,' he said, which probably will occur 'late Monday'.

'We've got ... boots on the ground, eyes on the ground. So before that, even before we can get into the air, before we can get boats on the water, we do have people on the ground to make sure that we're doing everything that we can to save every single life.'

Meanwhile, Mr Jindal told reporters there were unconfirmed reports that three critically ill patients died while being transported to safer ground.

'They had to weigh the risk between sheltering in place and evacuating and made the decision they thought was best for their patients,' he said. -- AFP

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