Hurricane Gustav is on a collision course with the U.S. Gulf Coast and is expected to hit Louisiana midday Monday. Up to 18,000 New Orleans residents have boarded buses and trains to escape the city.

New Orleans Mayor Ray Nagin warned that anyone staying behind to loot homes would face the full force of the law. The city is under a mandatory evacuation order and Nagin has also ordered a dusk-to-dawn curfew to prevent robberies.

"Looters will go directly to jail. You will not get a pass this time," Mayor Ray Nagin told reporters on Sunday. "You will not have a temporary stay in the city. You will go directly to the Big House."

The evacuation order became mandatory at 8 a.m. local time on Sunday for the more vulnerable west bank of the Mississippi River, and starts at noon on the east bank.

Police and Louisiana National Guard troops remain behind to patrol evacuated neighbourhoods. "We will have unprecedented security," Nagin promised.

CTV's Marcia MacMillan told CTV Newsnet from New Orleans that every street corner of the abandoned city seemed to have a police officer or National Guard member on it, available to help the few remaining citizens.

"It feels like a ghost town . . . many buildings have been boarded up, there's hardly anyone on the road, except for some police and the National Guard," she said Sunday evening.

MacMillan said that all stores and gas stations appeared to be closed.

Three years ago, hurricane Katrina swamped the city's flood defences. Much of New Orleans is below sea level. More than 1,800 people died and property damage ran into the billions of dollars. Social chaos followed, with widespread looting and other crime occurring in Katrina's immediate aftermath.

Many neighbourhoods still aren't rebuilt, and there are questions whether the city's levees and other defences can withstand another major hurricane.

The U.S. National Hurricane Center in Miami has issued a hurricane warning for an area from Cameron, La. eastward about 800 kilometres to the Alabama-Florida border.

New Orleans and Lake Ponchartrain are included in that zone. But a hurricane watch also extends east of Cameron into Texas.

"Preparations to protect life and property should be rushed to completion," the center advised.

Alabama also issued mandatory evacuation orders for some of its coastal areas. U.S. President George Bush also urged all Gulf Coast residents to evacuate, warning the flooding risk was considerable.

Gustav is currently rated as a Category 3 hurricane with sustained winds of 185 kilometres per hour, but forecasters believe it may regain strength and become a Category 4 storm as it passes over the warm waters of the Gulf of Mexico.

At 11 p.m. ET, it was located about 360 kilometres southeast of New Orleans, moving northwest at 26 kilometres per hour.

Nagin said his officials hope the hurricane, if it hits New Orleans, will move out quickly. The city's pumps can remove 2.5 centimetres of rainfall per hour for the first two hours, then capacity falls by about half, he said.

Gustav could drop up to 30 centimetres of rain, with 50 centimetres possible in some areas, forecasters say.

Cuba, the Gulf

Gustav was at Category 4 strength when it passed over Cuba with winds of 220 kilometres per hour, leaving homes and roads damaged or destroyed in its wake. However, while there were injuries, no deaths or serious injuries were reported.

Gustav made landfall at Los Palacios in the heart of the country's tobacco region.

Officials recorded gusts of 340 kilometres per hour in some areas of Cuba.

The hurricane has left 81 people dead so far, mainly by triggering floods and landslides in Haiti, the Dominican Republic and Jamaica.

In advance of the storm, oil and gas companies started shutting down their operations in the Gulf of Mexico. The U.S. Minerals Management Service said Saturday that more than three-quarters of all oil production and 40 per cent of gulf natural gas facilities were shut down.

The Gulf represents about one-quarter of U.S. oil production. Analysts say a prolonged shutdown would drive prices up for gasoline and other petroleum products.

Meanwhile, Tropical Storm Hanna is approaching the Turks and Caicos Islands and is expected to land either late Sunday or on Monday. It is expected hit the Bahamas and possibly Cuba in the coming days.

Hanna has sustained winds of 75 km/h. The hurricane center said it could lead to dangerous rip currents off some parts of the southeastern U.S. coastline.

With files from The Associated Press