BOONE'S CHAPEL, Ala. - Vicious storms and howling winds smacked the U.S. South, killing at least seven people in Alabama including three family members whose homes were tossed into nearby woods.

In Alabama's Washington County, about 50 miles (80 kilometres) north of Mobile, a mother and her two children were among those killed, said state emergency management agency director Art Faulkner. One person was reported dead in Mississippi's Greene County.

Combined with earlier reported fatalities in Arkansas and Oklahoma, the confirmed death toll had risen to 17 by early Saturday -- the nation's deadliest storm of the season.

Henley Hollon said Saturday that his 65-year-old brother, Willard Hollon, lived across the street from him in the Boone's Chapel community about 25 miles (40 kilometres) from Montgomery. Henley Hollon said Willard Hollon and Willard's two adult children, Steve and Cheryl, were killed when the storms roared through.

Henley Hollon said he had been watching the weather forecast on television -- and thought the worst was over when the winds started to pick up.

"It got up real fast. The lights went out," he said. "We had to feel our way into the hall. It lasted less than a minute."

He then went outside to check on the limbs down in his yard and walked across the road to check on his brother.

"When I shined the light out there I could see it was all gone," Henley Hollon said. Two mobile homes had been ripped from their foundations, and all that remained Saturday morning were wooden steps and flowerbeds.

"The trailer was anchored down and the anchors are gone," said Autauga County Chief Deputy Sheriff Joe Sedinger. "But the steps are still there and the blooms are still on the flowers."

Seven people were hurt in the storm, including a firefighter injured during the emergency response, Sedinger said. He said the storm hopscotched for several miles (kilometres), leaving some areas devastated and others untouched.

Another three deaths were reported early Saturday in Washington County in southern Alabama, said Yasamie Richardson, spokeswoman for the Alabama Emergency Management Agency.

The system had already destroyed or damaged dozens of homes, businesses and churches Friday afternoon in Mississippi, where crews worked to clear roads, find shelter for displaced families and restore power.

Jeff Rent, a spokesman for the Mississippi Emergency Management Agency,said one death was reported in Greene County. He did not have further details, and the Greene County Sheriff's Office did not immediately return a phone message Saturday.

In Marengo County in west-central Alabama, four separate tornadoes hit over the span of about five to six hours, emergency management director Kevin McKinney said.

A mobile home that had been tossed was a pile of rubble, along with another 30 homes or businesses that were destroyed, McKinney said. Four people had minor injuries.

Alabama Gov. Robert Bentley declared a state of emergency for the entire state, and the first race of a busy weekend at the Talladega Superspeedway was postponed until Saturday morning.

The storms began late Thursday in Oklahoma, where at least five tornadoes touched down and two people were killed. The system then pushed into Arkansas, killing seven more. Dozens of others were hurt.

By midday Friday, the storms had marched into Tennessee, Louisiana and later into Georgia. At least three twisters touched down in Mississippi, where a state of emergency was declared in 14 counties, causing widespread damage but only one serious injury.

The hardest hit was Clinton, a city of about 26,000 people just west of Jackson, the state capital. At least seven people were taken by ambulance to hospitals with injuries.