More than 1,500 homes, buildings and churches were damaged or destroyed across a wide area of central Florida north of the tourism region around Orlando. But two of the area's biggest attractions, Walt Disney Co.'s Disney World and Universal Studios Florida, were not affected.

Rescue teams fanned out to search for people who might still be trapped under flattened homes.

Crunched cars were flung onto porches, and battered sofas and fridges stood in piles of debris scattered over the exposed concrete foundations of houses. Dusk till dawn curfews were put into effect in two areas to deter looters.

The storm hit at 3:15 am (0815 GMT) and a spokesman for the Lake County sheriff's office said at least one and perhaps two tornadoes touched down in a state that ranks only behind the infamous "Tornado Alley" in the US Midwest for the number of tornado strikes. Most, such as a twister near Orlando on Christmas Day last year, cause no fatalities.

"The death toll is up to 19 now," said Kevin Lenhart, spokesman for the Lake County emergency operations centre. Another 19 people were in hospital.

The emergency centre said six were killed in Lady Lake, about 40 miles northwest of Orlando, and 13 in nearby Paisley, on the edge of the Ocala National Forest.

Pastor Howard Roszak of the First Baptist Church in Paisley said two teenage boys who belonged to his church were killed. One of the boys died along with his father, while both parents of the other teen were killed.

"I know all these kids real good. I love these kids. I hear there is nothing left ... just absolutely nothing," Roszak said, referring to the home of one of the boys.

Sen Bill Nelson, a Florida Democrat, compared the devastation to a "total war zone about 300 yards wide, about three football fields."

"The last thing we saw before lifting off was a little fawn whose rear leg was just dangling, limping off on three legs into the woods," he said after a helicopter tour.

About 1,000 tornadoes hit the United States annually, killing on average 80 people a year, and winter tornadoes appear to be more prevalent during El Nino years, when the waters of the eastern Pacific become unusually warm.

"This is something that we've seen here in the past in our state when we've had El Nino conditions in place," said state meteorologist Ben Nelson.

In February 1998, another El Nino year, a swarm of tornadoes killed more than 40 people in central Florida and injured scores more. One narrowly missed the crowded tourist area that includes Disney, Universal Studios and Sea World.

The National Weather Service said it believed more than one tornado touched down on Friday but had yet to ascertain that.

Florida Highway Patrol spokeswoman Kim Miller said the tornado blew over five tractor-trailer rigs at about 3:45 a.m.

"We saw tractor-trailers littered all over the interstate," she told CNN. "We had a few cars mixed into that."

The storm knocked out power to more than 42,000 customers but only 7,800 were still without electricity by mid-afternoon, an official with the local utility, Progress Energy, said.

Florida Gov. Charlie Crist declared a state of emergency in four affected counties and the Red Cross opened shelters for people left homeless.