A wave of tornado-spawning storms strafed the U.S. South on Wednesday, splintering buildings across hard-hit Alabama and killing 72 people in four states.

At least 58 people died in Alabama alone, including 15 or more when a massive tornado devastated Tuscaloosa. The city's mayor said sections of the city that's home to the University of Alabama have been destroyed and the city's infrastructure is devastated. 

Eleven deaths were reported in Mississippi, two in Georgia and one in Tennessee.

News footage showed paramedics lifting a child out of a flattened Tuscaloosa home, with many neighbouring buildings in the city of more than 83,000 also reduced to rubble. A hospital there said its emergency room had admitted at least 100 people.

mi-steeple-00576698

People walk through debris after a tornado hit downtown Culman, Ala., on Wednesday. ((Butch Dill/Associated Press))

"What we faced today was massive damage on a scale we have not seen in Tuscaloosa in quite some time," Mayor Walter Maddox told reporters, adding that he expected his city's death toll to rise.

The storm system spread destruction Tuesday night and Wednesday from Texas to Georgia, and it was forecast to hit the Carolinas next and then move further northeast. 

Around Tuscaloosa, traffic was snarled Wednesday night by downed trees and power lines, and some drivers abandoned their cars in medians.

University officials said there didn't appear to be significant damage on campus, and it was using its student recreation centre as a shelter.

Maddox said authorities were having trouble communicating, and 1,400 National Guard soldiers were being deployed around the state.

Brian Sanders, the manager of an oil change shop, brought his daughters to DCH Regional Medical Center because he felt they'd be safe there. He said his business had been levelled. 

"I can't believe we walked away," he said.

Stunning damage

Storms struck Birmingham earlier in the day, felling numerous trees that impeded emergency responders and those trying to leave hard-hit areas. Surrounding Jefferson County reported 11 deaths by late Wednesday; another hard-hit area was Walker County with eight deaths. The rest of the deaths were scattered around the state, emergency officials said.

Austin Ransdell and a friend had to hike out of their neighbourhood south of Birmingham after the house where he was living was crushed by four trees. No one was hurt. 

As he walked away from the wreckage, trees and power lines crisscrossed residential streets, and police cars and utility trucks blocked a main highway.

"The house was destroyed. We couldn't stay in it. Water pipes broke; it was flooding the basement," he said. "We had people coming in telling us another storm was coming in about four or five hours, so we just packed up."

Not far away, Craig Branch was stunned by the damage.  

"Every street to get into our general subdivision was blocked off. Power lines are down; trees are all over the road. I've never seen anything like that before," he said

In Huntsville, meteorologists found themselves in the path of tornado and had to evacuate the National Weather Service office.

On Wednesday morning, a Louisiana police officer on a camping trip in Choctaw County, Miss., was killed when a towering sweetgum tree fell onto his tent as he shielded his young daughter with his body, said Kim Korthuis, a supervisor with the National Park Service. The girl wasn't hurt. 

The nine-year-old girl was brought to a motorhome nearby where campsite volunteer Greg Maier was staying with his wife, Maier said. He went back to check on the father and found him dead.

"She wasn't hurt, just scared and soaking wet," Maier said.

Her father, Lt. Wade Sharp, had been with the Covington Police Department for 19 years.

"He was a hell of an investigator," said Capt. Jack West, his colleague in Louisiana.

Downed trees impede emergency crews

Also in Mississippi, a man was crushed in his mobile home when a tree fell during the storm, a truck driver died after hitting a downed tree on a state highway and a member of a county road crew was killed when he was struck by a tree they were removing.

Four more Mississippi storm deaths were reported late Wednesday, but the circumstances weren't immediately clear. The governor also made an emergency declaration for much of the state.

In Alabama, one woman died when her mobile home was torn to shreds, and a second woman was trapped under a mobile home elsewhere. Falling trees or limbs also killed a woman in her house, a man standing outside and a motorist in separate locations.  

In both Mississippi and Alabama numerous felled trees blocked roads, impeding emergency responders and those trying to leave hard-hit areas.

Austin Ransdell and a friend had to hike out of their neighborhood south of Birmingham after the house where he was living was crushed by four trees. No one was hurt.

As he walked away from the wreckage, trees and power lines crisscrossed residential streets, and police cars and utility trucks blocked a main highway.

"The house was destroyed. We couldn't stay in it. Water pipes broke; it was flooding the basement," he said. "We had people coming in telling us another storm was coming in about four or five hours, so we just packed up."