New Orleans, Louisiana - Hurricane Gustav lashed the US state of Louisiana with torrential rain and gale force winds on Monday after forcing nearly two million people to flee.
Fearing a repeat of the Hurricane Katrina disaster, hundreds of troops were sent into New Orleans after what is being called the biggest evacuation in United States history.
Three critically ill people were reported to have died as they were being moved from the danger zone. Oil production platforms were shut down, the Republican party suspended the start of its presidential election convention and President George Bush headed for Texas to monitor emergency preparations for Gustav which has killed more than 80 people in Dominican Republic, Haiti and Jamaica.
Reports of power outages in New Orleans started after wind and rain began hitting the city - still struggling from Katrina, which struck almost exactly three years ago.
Louisiana officials said there were about 750 National Guard troops in New Orleans if a new rescue operation was needed. Mayor Ray Nagin on Sunday ordered a curfew and vowed to throw looters into prison.
The edge of the storm has crossed the Mississippi Delta, lashing New Orleans, said National Hurricane Centre meteorologists.
At 09h00 GMT (about 11am SA time), the eye of the hurricane was 185 kilometres southeast of New Orleans moving towards the coast at 26km an hour.
Storm force winds from Gustav extended as far as 370km from the eye, the centre said.
A category three hurricane, Gustav packed sustained winds of 185km per hour.
"No significant change in strength is likely before landfall," the US National Hurricane Centre said in its latest advisory.
"This is a serious storm," Louisiana Governor Bobby Jindal said in a final appeal to the people who remained in New Orleans despite government warnings.
People in the state capital of Baton Rouge and other inland areas have been warned to watch for storm-spawned tornados.
Gustav forced US President George 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 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 from St. Louis, after returning from a tour of relief preparations in Mississippi.
Military and civilian disaster relief operations were prepared, with memories still fresh of the destruction wrought by Katrina, and the government's 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.
New Orleans mayor Nagin 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," 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 rescue teams were 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."
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.