A tornado struck Madison County in the US state of Iowa on Saturday, killing four adults and two children, according to officials.

At least four other adults were injured in the tornado that caused "widespread damage to both homes and properties," the county's emergency management director told a press briefing.

"This is, I think, the worst that anyone has seen in quite a long time," Diogenes Ayala said. "This will be impactful for many years to come."

National Weather Service (NWS) Des Moines tweeted at 7:30 pm (0130 GMT Sunday) that "the worst is over for central Iowa." 

3/5/2022 7:30PM UPDATE: Thankfully, the worst is over for central Iowa. Storms are moving off to the East. Areas west of the line, including the Des Moines metro, are in the clear.

— NWS Des Moines (@NWSDesMoines) March 6, 2022

On Sunday, the NWS stated its survey teams would properly evaluate the damage.

"This is pretty devastating for our community," Ayala said, adding that rescue efforts would continue overnight.

Governor Kim Reynolds of Iowa has declared a disaster in Madison County, allowing state resources to be used to aid in recovery.

"Our hearts go out to all those affected by the deadly storms that tore through our state today," Reynolds said in a statement. 

Hundreds of tornadoes slammed through five US states overnight in December, killing at least 79 people in Kentucky, as well as fatalities in Tennessee, Arkansas, Missouri, and Illinois.