Gustav just short of becoming a top-scale Category 5 hurricane

Gustav slammed into Cuba's tobacco-growing western tip as a monstrous Category 4 hurricane Saturday while both Cubans and Americans scrambled to flee the storm as it roared toward the oil-rich Gulf of Mexico and New Orleans.

Forecasters said Gustav was just short of becoming a top-scale Category 5 hurricane as it hit Cuba's mainland after passing over its Isla de la Juventud province, where shrieking 150 mph (240 kph) winds toppled telephone poles, mango and almond trees and peeled back the tin roofs of homes.

Meanwhile on the Gulf Coast authorities began ordering mandatory evacuations along Louisiana and Mississippi's Gulf Coast on Saturday as Hurricane Gustav roared past Cuba and into the Gulf of Mexico.

"They made it very clear that this storm could be as bad as it gets," Louisiana Gov. Bobby Jindal said Saturday afternoon of the Category 4 storm, with sustained winds that reached 150 mph. "We could see flooding even worse than we saw in Hurricane Katrina."

Thousands of people had begun fleeing the coast by the time a hurricane watch was issued Saturday afternoon for southeastern Texas to the Alabama-Florida border as Gustav pursued a projected path toward the U.S. Gulf Coast.

The watch, which means hurricane conditions are possible within 36 hours, was announced the day after many in the region marked the third anniversary of Katrina's landfall.