Seven people, including two children, have been killed by a tornado that struck a state in the US.

The tornado ripped through Madison County, which is southwest of the state capital Des Moines, in Iowa, on Saturday, the Des Moines Register reported, citing local officials.

The heavy storms caused more than 10,500 people in Des Moines to lose power.

The National Weather Service added the tornado was an EF3, meaning that it swirled with winds of up to 206 miles per hour (332 kph).

It was an “extremely dangerous” situation, the agency tweeted.

US reports initially indicated that two people had been killed when the tornado struck Winterset and nearby communities.

But Madison County emergency management director Diogenes Ayala later confirmed that four children and two adults had been killed when the twister hit around 4.30pm local time (10.30pm GMT).

She added the two children who died were under the age of five.

He said: “This is, I think, the worst anyone has seen in quite a long time.”

Mr Ayala added the tornado also left one adult with life-threatening injuries and three others in a serious condition in hospital.

He said that “this is a widespread storm”, before estimating there was serious damage to more than two dozen homes.

Iowa Governor Kim Reynolds issued a a statement saying she and her husband are praying for those who had died and also those injured in the tornado.

She said: “Our hearts go out to all those affected by the deadly storms that tore through our state today.

“Our hearts ache during this time, but I know Iowans will step up and come together to help in this time of need – they already are.”