Hurricane Ivan veered to the north Wednesday on a path toward Alabama's Gulf Coast as inhabitants across a 300-mile-wide danger zone braced for its onslaught, and a new storm gathered strength in the Caribbean.

The hurricane, which has forced evacuation orders for more than 2 million people in four states, claimed its first American victims Wednesday after killing at least 68 people on its rampage through the Carribean.

Tornadoes spawned by the storm killed two people in Panama City, a resort town in the Florida Panhandle.

In Louisiana, a cancer patient and a nursing home resident died in traffic while they were being evacuated to higher ground.

The National Hurricane Center in Miami had warned that the giant, Category Four storm could spawn isolated tornadoes beginning late this afternoon in southern Louisiana, Alabama, the Florida Panhandle and southwestern Georgia. But the hurricane's greatest effects were expected to be flooding.

In its latest advisory, issued at 7 p.m. Eastern time, the hurricane center said the eye of the storm was about 105 miles south of the Alabama coastline and was expected to reach land late Wednesday or in the early hours of Thursday. The storm was packing maximum sustained winds of 135 mph, the advisory said.

Just before 6 p.m., Ivan blasted 100 mph, hurricane-force winds onto the fragile marsh towns at the toe-tip of Louisiana's distinctive boot-shaped frame.

The storm inflicted its first damage in towns, such as Venice, La., which are connected only by spindly, poorly-lighted roads to the more populated New Orleans area. Power was knocked out to nearly half the residents of lower Plaquemines Parish, a region that fishermen and oil drillers have used for decades as a launching point for forays into the Gulf of Mexico.

Plaquemines Parish President Benny Rousselle said about 10,000 customers between Port Sulphur and Venice had already lost power by 5 p.m. He said the Venice area was already reporting hurricane-force winds, even though the eye wall was still far off to the southeast, and the strongest gusts were expected northwest of the eye.

"We're on the good side, if you can call it a good side," Rousselle said. "But we're already hearing about roof damages, and trees blocking the roads. The levees have held so far, but I don't like to say that too loud."

Mobile, Ala., was bracing for a battering that forecasters said could inundate a large section of the city. The Gulf port city is expected to take one of the heaviest hits from a storm that has forced evacuations from the fishing towns near Apalachicola, Fla. to the tony fine dining meccas of New Orleans's French Quarter.

Powerful waves kicked up by the outer edges of the hurricane were already tossing broken posts and shards of oyster boats onto Dauphin Island, at the mouth of Mobile Bay, at 3 p.m. Water sloshed over the floor of Pelican Reef, a popular restaurant at the Fowl River Marina. Ivan hinted at its strength by sending strong gusts through Mobile.

In a city that is long accustomed to the destructive force of hurricanes preparations for Ivan were still being made, even as the gigantic storm loomed off the coast, just hours from landfall. The sound of hammers on plywood filled streets in the city's compact downtown. In Mobile County, three shelters were filled to capacity, and many of the area's nearly 400,000 residents boarded up their homes. More than 100,000 were asked to evacuate. Emergency managers believe almost half of those people -- far more than usual -- have fled north in search of higher ground.

"People are taking this more seriously than before because of the recent storms in Florida," said Lt. Richard Caytom of the Mobile County Sheriff's Department.

To the west, New Orleans breathed a sigh of relief that the hurricane was no longer heading straight for the low-lying city, but Mayor Ray Nagin warned that Ivan's wide arc of hurricane-force winds could still cause some damage.

"We're still in the cone of certainty," he told a news briefing. "We're not quite out of the woods, but the storm has moved northerly, which gives us some cause for some relief." Although New Orleans now appears likely to be "grazed by hurricane-force winds," Nagin said, "we're still facing serious winds in the next hours."

The city, parts of which are as much as 10 feet below sea level, ordered a mandatory evacuation and imposed a 2 p.m. curfew as Ivan approached, and thousands of people clogged the roads as they fled to higher ground. The 1.2 million inhabitants of metropolitan New Orleans were among nearly 2 million people who were ordered to evacuate vulnerable locations in Louisiana, Mississippi, Alabama and Florida.

A hurricane warning was in effect Wednesday from Grand Isle, La., to Apalachicola, Fla., a stretch of territory including the greater New Orleans area and Lake Pontchartrain, the National Hurricane Center reported.

After one of the largest evacuations in the history of New Orleans, the historic French Quarter was almost completely boarded up, its renowned restaurants closed. Here and there before the curfew, a few tourists still walked the streets, taking pictures of each other. With the city's Louis Armstrong Airport shut down since Tuesday night in anticipation of the hurricane, many tourists were unable to leave, finding themselves stuck with those residents who lacked cars or other means of transportation to enable them to flee.

As Ivan churned toward a U.S. landfall, the U.S. Coast Guard ordered the closure of five ports in Alabama, Florida and Mississippi and said vessels would need permission to move along the southern end of the Mississippi River in Louisiana after 1 p.m. EDT.

Oil companies shut down some refineries and oil rigs in the Gulf of Mexico and evacuated thousands of workers from offshore platforms.

According to the U.S. Census Bureau, more than 6 million people could be affected by Ivan.

Eric Blake, a meteorologist at the National Hurricane Center, said hurricane-force winds would cut a swath at least 100 miles wide, hitting a broader area than either of this season's preceding two major hurricanes, Charley and Frances.

"This storm is three times the size of Charley at least," he said. "It's larger than Frances and it's as strong as Charley. This is the most significant threat that the United States has seen since Hurricane Andrew."

According to the National Oceanic and Atmospheric Administration, Hurricane Andrew, which struck Florida in August 1992, ranks as the most destructive U.S. hurricane on record. With peak gusts of more than 160 mph, it caused 23 deaths in the United States and three in the Bahamas, leaving damage estimated at $26.5 billion in Florida and Louisiana.

As Ivan made its way north at about 14 mph, forecasters were also watching another system, Tropical Storm Jeanne, which was gathering force in the Caribbean.

The National Hurricane Center declared a hurricane warning for Puerto Rico and the Virgin Islands as Jeanne moved west-northwest at about 10 mph with sustained winds near 65 mph.

The center of the storm made landfall on Puerto Rico near Yabucoa on Wednesday and moved over the central and western parts of the island during the afternoon and evening on its way back into the Atlantic Thursday, the hurricane center said. As of 8 p.m., the storm was about 90 miles east of the Dominican Republic.

Forecasters said the storm could strengthen as it moves into the Atlantic and could become a hurricane later Wednesday night or Thursday.

Branigin reported from Washington. Staff writer Catharine Skipp in Mobile contributed to this report.