Severe storms and tornadoes along the US Gulf Coast killed at least three people and injured 30 on Tuesday, destroying buildings and other structures across several states.

Two people died in Louisiana when a storm hit their mobile home park in St. James Parish, 50 miles (80 kilometers) west of New Orleans, said parish government personnel manager Libby Hotard.

The region was among the worst hit. "Some areas are totally devastated," Hotard told AFP.

A man who lived near the mobile home park told local television station WVUE that he was asleep when he heard a "big rumbling sound and the whole entire house started shaking."

Video broadcast on local television showed mobile homes completely destroyed by the storms.

Emergency services transported 30 injured to local hospitals, Hotard said. Rescuers were conducting search and rescue operations.

Another man died in the neighboring state of Mississippi when a storm smashed into his mobile home 100 miles north of New Orleans, county Emergency Management Director James Smith said.

There were no reports of other deaths or injuries in the area.

The National Weather Service said a tornado hit southern Mississippi and that officials were tracking reports of other possible tornadoes in the region.

Mississippi Governor Phil Bryant declared a state of emergency for areas expected to be hit by the storm.

Across the Gulf Coast region, the storms damaged buildings, blew off roofs and downed power lines and trees -- sometimes with golfball-sized hail -- local media reported.

Forecasters said at least 20 million people are at risk from the storms and tornadoes into Wednesday.

The National Weather Service is predicting severe thunderstorms with damaging winds and some tornadoes from eastern Louisiana to Alabama.

The storms hit Texas early Tuesday before moving east during the afternoon. They are expected to continue through Florida, Georgia, the Carolinas and eastern Virginia on Wednesday.