Powerful tornadoes raked across a wide swath of the US Midwest and South on Friday, killing at least 27 people in three states and bringing the death toll to at least 40 from a week of deadly late-winter storms.

The twisters splintered homes, damaged a prison and tossed around vehicles across the region, leaving at least 13 people dead in southern Indiana, another 12 in neighboring Kentucky and two more in Ohio, officials said. In all, the latest line of storms battered a band of states from Ohio and Indiana on southward to Alabama.

"We are no match for Mother Nature at her worst," Indiana Governor Mitch Daniels said in a statement, adding that he would visit the stricken southeast corner of the state on Saturday.

Another possible storm-related death occurred in Henryville, Indiana, where television images showed homes blown apart.

Televised video taken from the air showed rescue workers in Indiana picking through one splintered house, residents sifting through the ruins of a home, and a school bus thrown into a building. Several warehouse-like structures had their roofs ripped off.

Major Chuck Adams of the sheriff's office in Indiana's Clark County said there was extensive damage to a school in Henryville but said: "All the children are out. No injuries to any of them, just minor scrapes and abrasions."

An Indiana official confirmed 13 deaths from the tornadoes on Friday, in four southeastern counties. A spokesman for Kentucky's Department of Public Health reported a statewide death toll of 12, while Ohio officials said there were two deaths in a single county.

"There's a possibility we could have additional fatalities," in southwestern Ohio said Kathy Lehr, the director of public information in Clermont County.

The Ohio victims were a 54-year-old man and a 64-year-old woman who was a city council member in the town of Moscow, Lehr said. Many homes in the county had suffered damage, including some in which buildings were swept off their foundations.

Storm warnings were issued throughout the day from the Midwest to the Southeast, and schools and businesses were closed ahead of the storms after a series of tornadoes earlier in the week killed 13 people in Kansas, Missouri, Illinois and Tennessee.

"We may not be done yet," said John Hart, a meteorologist at the Weather Service's Storm Prediction Center in Norman, Oklahoma.

As night fell and temperatures cooled, the line of storms appeared to weaken somewhat as they traveled eastward, but the National Weather Service warned of another possible outbreak of tornadic weather in Saturday's early hours.

Severe thunderstorms and tornadoes were likely over an area stretching from Indiana and Ohio into Kentucky, Tennessee, Mississippi and Alabama.

This week's violent storms raised fears that 2012 will be another bad year for tornadoes after 550 deaths in the United States were blamed on twisters last year, the deadliest year in nearly a century, according to the Weather Service.

The highest death tolls were from an April outbreak in Alabama and Mississippi that claimed 364 lives, and from a May tornado in Joplin, Missouri, that killed 161 people. There were two tornado-related deaths earlier this year in Alabama.

Alabama's Madison County, which was struck by a tornado during last April's deadly outbreak, was hit again on Friday by a tornado that took a similar path. An emergency management official said seven people had been transported to hospitals.

"There were two storms that moved across the area, very close together, almost attached to each other," National Weather Service meteorologist Chris Darden said. The Weather service said the damage was from an EF-2 tornado with winds of 120 miles per hour that took a similar path to a devastating tornado on April 27, 2011.

Authorities said 40 homes were destroyed and 150 damaged in two northern Alabama counties on Friday.

A prison, Limestone Correctional Facility, was in the path of the storm, Alabama officials said. High winds caused roof damage to two dormitories, forcing 300 inmates to be moved to elsewhere in the facility.

No one was seriously injured at the prison and there were no risks of prisoners escaping, though there was damage to some perimeter fencing and a canteen, said Brian Corbett, a spokesman for the Alabama Department of Corrections.

Multiple tornadoes also struck Tennessee and along the Ohio River valley in Illinois, Indiana and Kentucky.

In Kentucky, a small trailer park, a fire station and a few homes in Trimble County were destroyed by suspected tornadoes about 40 miles (63 km) northwest of Louisville, the Kentucky State Police said. The fire house and trailer park in Milton "were down to the ground," said the state police's Kevin Woosley.

Nashville was pounded by rain and hail, and suspected tornadoes struck twice, hours apart, in eastern Tennessee near Chattanooga. Among the places hit was the valley below historic Lookout Mountain.

"We've had 29 injuries in the state, but no fatalities," said Dean Flener of the Tennessee emergency management agency.

Storm damage to transmission lines in Tennessee forced operators to reduce the output of the Tennessee Valley Authority's 1,126-megawatt Unit 2 at the Sequoyah nuclear plant to 70 per cent from full power, a spokeswoman said.

More than 57,000 customers served by providers in the TVA service area were without power in north Alabama, western Kentucky and southeast Tennessee, the power supplier said.

High winds downed power lines in the Atlanta area, pitching more than a thousand homes into darkness, and officials warned residents about torn lines becoming entangled in trees.