HAVANA — Gustav swelled into a fearsome Category 4 hurricane with winds of 145 mph (235 kph) on Saturday as Cuba raced to evacuate more than 240,000 people and Americans to the north clogged highways fleeing New Orleans.

It could become a Category 5 storm over the Gulf of Mexico by Sunday, with winds of 160 mph (255 kph) according to the U.S. National Hurricane Center in Miami. Gustav already has killed 81 people in the Caribbean and it was on a course for the Katrina-battered U.S. coast.

Cuba grounded all national airline flights, though planes bound for international destinations were still taking off at Havana's Jose Marti International Airport. Authorities also canceled all buses and trains to and from the capital, as well as ferry and air service to the Isla de Juventud, the outlying Cuban island-province next in Gustav's path.

Heavy winds had already felled mango and almond trees and were shaking the roofs of buildings in the province, said Ofilia Hernandez, who answered a community telephone near downtown Nueva Gerona, Isla de la Juventud's largest city.

"Everyone's at home. It's getting very ugly," she said. "All night last night there was wind, but not like now. Now it's very strong. Things are starting to fall down."

The government's AIN news agency said officials were evacuating some 190,000 people from low-lying parts of tobacco-rich Pinar del Rio province on the western tip of Cuba's main island. AIN reported that 50,000 already had been evacuated further east.

Stiff winds whipped intermittent rains across Havana, where police officers in blue and orange rain coats supervised workers removing stones, tree branches and other debris from the storied beachfront Malecon, as angry waves crashed against the sea wall below.

Some shuttered stores had hand-scrawled "closed for evacuation" signs plastered to their doors. At others, small lines formed as residents stocked up on bread. Cars waiting to fill up their tanks stretched into the street outside some gas stations.

"It's very big and we've got to get ready for what's coming," said Jesus Hernandez, a 60-year-old retiree who was using an electric drill to reinforce the roof of his rickety front porch.

The U.S. naval base at Guantanamo, Cuba, was hundreds of miles (kilometers) to the east, out of the storm's path.

Gustav rolled over the Cayman Islands Friday with fierce winds that tore down trees and power lines while destroying docks and tossing boats ashore on Little Cayman Island, but there was little major damage and no deaths were reported.

Gustav's eye was centered close to the Isla de Juventud and about 110 miles (180 kilometers) south of Havana. It was expected to be moving northwest near 14 mph (22 kph).

Hurricane force winds extended out 70 miles (110 kilometers) in some places.

Haiti's Interior Ministry on Saturday raised the hurricane death toll there to 66 from 59. Jamaica upped its death toll to seven from four. Gustav also killed eight people in the Dominican Republic.

Gustav could strike the U.S. Gulf coast anywhere from the Florida Panhandle to Texas, but forecasters said there was an increasing chance that New Orleans will get slammed by at least tropical-storm-force winds, three years after devastating Hurricane Katrina.

People began pouring out of the city along the highways and the government announced plans for broader evacuations. The Federal Emergency Management Agency said it expects a "huge number" of Gulf Coast residents will be told to leave the region this weekend.

As much as 80 percent of the Gulf of Mexico's oil and gas production could be shut down as a precaution if Gustav enters as a major storm, weather research firm Planalytics predicted. Oil companies have already evacuated hundreds of workers from offshore platforms.

Retail gas prices rose Friday for the first time in 43 days as analysts warned that a direct hit on Gulf energy infrastructure could send pump prices hurtling toward $5 a gallon. Crude oil prices ended slightly lower in a volatile session as some traders feared supply disruptions and others bet the U.S. government will release supplies from the Strategic Petroleum Reserve.

Meanwhile, the hurricane center said Tropical Storm Hanna was projected to near the Turks and Caicos Islands late Sunday or on Monday, then curl through the Bahamas by early next week before possibly threatening Cuba.

It had sustained winds near 50 mph (85 kph) Saturday and the hurricane center warned that it could kick up dangerous rip currents along parts of the southeastern U.S. coast.