"We need to take this seriously, this is a deadly storm" said Florida Governor Jeb Bush, urging residents in threatened areas to board up their homes and seek shelter inland.

Most of Florida's densely populated east coast was placed under a hurricane warning, which means the storm could slam within 24 hours into the state that is still recovering from the devastation of Hurricane Charley earlier this month.

About 2.5 million people along south Florida's Atlantic coast were told to evacuate their homes and move to safer areas as Frances approached with sustained winds of 205 kilometers (125 miles) per hour and higher gusts.

"Preparations to protect life and property should be rushed to completion," said forecaster Lixion Avila of the Miami-based National Hurricane Center.

San Salvador Island in the Bahamas reported sustained winds of 190 kphmph) when the edge of the storm's eye passed over island before pounding Cat Island, also in the Bahamas, where a resident told a Florida radio station by telephone "the wind sounds like a freight train."

But there was a little good news as Frances lost some of her steam and was downgraded one point to a level-three hurricane on the Saffir-Simpson scale, which reaches a maximum of five.

But forecasters warned that Frances could regain strength.

At 23:00 pm Thursday (0300 GMT Friday), the eye of the storm was just off Cat Island and 530 kilometers (330 miles) southeast of landfall on the Florida coast. Hurricane-force winds extended 130 kilometers (80 miles) outward, the NHC said.

The storm was likely to hit Florida over the weekend, with tropical storm winds already expected on Friday.

"The consequences of not evacuating could be very severe," Miami-Dade Mayor Alex Penelas said after announcing a mandatory evacuation from threatened areas in the county. Residents in West Palm Beach and other areas got similar orders.

Penelas said that while there was no certainty the powerful hurricane would hit the area, "I'd rather be safe than sorry."

Long lines formed outside those gas stations that still had fuel, and stores were running out of basic supplies, including bottled water and batteries, as residents stocked up to ride out the storm.

A number of tourists were put up at emergency shelters after their hotels shut. Those hotels that remained open were packed to capacity.

Fort Lauderdale's international airport was scheduled to shut down early Friday, and the city's busy Port Everglades had already closed for both cargo and cruise ships.

Schools, office buildings and restaurants in South Florida also shut down, though some people braved the increasingly strong winds to enjoy a day at the beach.

Throughout the day, officials warned the impact of the storm could be massive.

"This is going to be, if this storm makes landfall in Florida, a very large, a very dangerous storm. We're going to have a lot of people in harm's way," Florida Emergency Management Director Craig Fugate said.

Florida is still recovering from the death and destruction wrought by Hurricane Charley in southwestern parts of the state.

Frances packs the same power as Charley but is about twice its size.

Several cruise ships diverted from their initial course to steer clear of the storm.

"We can't control the kind of damage that Frances is going to cause, but if people are smart, lives can be saved," said Max Mayfield, the NHC director.

Wednesday, Frances lashed the Turks and Caicos islands, damaging roofs, uprooting trees, causing power outages and downing telephone lines.

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