The Forrest County seat of Hattiesburg, Mississippi, and the adjacent town of Petal, both about 100 miles southeast of Jackson, the state capital, bore the brunt of storms that struck less than an hour before dark.
The tornado that plowed through the Hattiesburg area was believed to have reached three-quarters of a mile in diameter at times, said Anna Weber, a National Weather Service meteorologist.
The weather service counted three separate twisters in south-central Mississippi on Sunday evening, Weber said.
In neighboring southwestern Alabama, authorities reported a flurry of seven tornadoes across three counties, including one that damaged 46 homes in Clark County, Weather Service meteorologist Keith Williams said.
About 100 houses or more were damaged or destroyed in Petal, Mississippi, alone, and several businesses were hard hit there as well, including a hardware store reduced to rubble, Mayor Hal Marx told Reuters.
He said a number of residents suffered minor injuries but no one was reported seriously hurt. 'Mostly people are just shaken up and in shock,' he said.
Jeff Rent, a spokesman for the state Emergency Management Agency, said he had reports of at least 10 people injured throughout four stricken Mississippi counties, including eight who were taken to hospitals in Marion County.
Emergency management officials said no firm estimates of property losses were immediately available. Power outages were widespread.
University campus and high school hard hit
CNN broadcast photos of several homes in Hattiesburg badly mangled from the storm, some with roofs and exterior walls ripped open.
Emergency management spokesman Greg Flynn said a search-and-rescue team from the nearby town of McComb was being called in to help look through debris for anyone who might be trapped.
On the Hattiesburg campus of the University of Southern Mississippi, alma mater of retired National Football League star quarterback Brett Favre, the storm damaged several buildings, including a performing arts center and an alumni house, the university said in a statement.
The twister also heavily damaged a high school stadium complex and blew a truck onto the school's baseball diamond, officials said.
Kris Walters, 40, a Baptist minister for the USM campus, said he and two of his children took shelter in a closet with a mattress on top of them until the storm passed, adding that his house escaped serious damage.
'I have lived here 40 years, and this is the first tornado I have ever seen like this,' he told Reuters.
Joby Bass, a university professor interviewed on CNN, said the porches on his house 'peeled off' and trees toppled onto his roof as he and his dogs huddled in a closet for safety.
'A lot of houses on this street are completely roofless,' Bass said. He said the campus was largely empty because students had an extended weekend to celebrate Mardi Gras. The university said no injuries were reported on campus.
Video footage showed what appeared to be a large, gray tornado, filmed from a distance, churning through town as a cloud of debris swirled around it.
Rent, the state emergency management spokesman, said Mississippi Governor Phil Bryant had declared a state of emergency in four Mississippi counties - Forrest, Lamar, Marion and Lawrence - and other areas hit by the storms.
The Hattiesburg area also suffered heavy property damage from Hurricane Katrina in 2005.