At least six people have been injured after several tornadoes ripped through Iowa, with the fierce storms leaving a path of destruction in their wake.

In Pella in the state's south-east, a company that manufactures industrial and agricultural equipment reported "major damage" after one tornado hit.

Linda Parker, a spokeswoman for the Iowa Department of Homeland Security and Emergency Management, said seven people were treated at the scene with six taken to hospital.

Another tornado hit the city of Marshalltown overnight. There were no immediate reports of injuries, but there were reports of several tornadoes in the area, which is located about an hour north-east of Des Moines.

Pictures from the damaged areas show trees crashed down on to roads and roof tiles ripped away from homes.

City Administrator Jessica Kinser said the damage forced Marshalltown officials to declare a state of emergency.

"Everyone is advised to stay away from downtown Marshalltown until further notice," she said in a statement.

"We also ask that people stay off cell lines unless necessary, to allow for emergency phone traffic."

About 27,000 people live in the town. Many of them were without power - Alliant Energy reported 6,690 homes and businesses were without electricity.

According to CNN affiliate WOI, another tornado damaged houses in Bondurant, about 15km from Des Moines.

The storm knocked out power and telephone service at city hall in the town.