"It's amazing to see how destructive and how surgical -- the intensity of a tornado," said Charlie Crist, governor of Florida, which has seen many hurricanes.

He also declared an emergency in the four counties and said Florida residents have pulled together.

"They have poured out their hearts to help their fellow man," he told reporters.

Thirteen people died in Paisley and six in Lady Lake, Christopher Patton, a spokesman for Lake County, told AFP. CNN television reported 20 dead. The toll is not expected to rise.

"Our search and rescue are completed and we are now in the recovery stage, making sure we're getting needs met," Jennifer Stan with Florida emergency operations told AFP.

Some 1,500 homes were damaged or destroyed and an estimated 13,000 people were left without electricity after the storm, which uprooted trees and felled power lines.

The storms hit around 3:30 am (0830 GMT) Friday, as most people slept. Because few had any warning, many residents were stunned the toll was not higher.

Lake County school superintendent Anna Cowin said two of her students had been confirmed dead. "One family was hit with much tragedy. Both parents were killed. There are four in the family, and one of their children also died," she said.

A area of some 51 square kilometers (20 square miles) was ravaged by the storms.

Residents likened the storms to a freight train that roared and slammed into their homes.

"It woke me out of a dead sleep," local resident David Wholly told the Orlando Sentinel newspaper. "I heard the noise, and it sounded like a train coming, and I ran to the bathroom. The tree went right through the bedroom window where my head was."

Television images showed the ground littered with the debris of scores of homes, with residents sifting through the remains of their belongings. Many were in shock and desperate to find any souvenir, a family memento or a picture frame.

The Federal Emergency Management Agency, so criticized for its performance when Hurricane Katrina hit the Gulf Coast in 2005, made sure that Bush signed an emergency measure for the four Florida counties, releasing needed funds, said FEMA director David Paulison.

He said FEMA trailers were on their way with food, water and other supplies, but stressed that FEMA cannot work alone.

"It's neighbors helping neighbors," he said. "If we work together, we can do this."

Florida Representative Tom Feeney said a 30-person assessment team was in place "and trucks filled with water, food and ice are headed to the devastated areas."

Authorities opened shelters for those left homeless.

The Lady Lake Church of God was completely destroyed, an AFP photographer said. Parishioners said they hoped to hold a service Sunday, under the open sky.

Experts said the severe weather was spawned by El Nino, which occurs when water in the eastern Pacific Ocean becomes unusually warm and can trigger storms over the southern United States.

"This was a pretty classic El Nino event," said Robert Molleda, National Weather Service warnings coordinator for South Florida.

Friday's storms struck on the ninth anniversary of Florida's ferocious "Groundhog Day Storm" of 1998, when seven tornadoes and fierce storms killed 42 people in Florida.

In December, more than a dozen people were injured and more than 200 homes destroyed when storms and tornadoes ripped through the same area of central Florida.

The area of devastation is northwest of the Walt Disney World Resort, which was not affected by the bad weather.

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