Whole buildings have been torn apart, as Wendy Urquhart reports. Photo: BBC

Sixteen of the victims were in several suburbs of Little Rock in Arkansas, officials said.

One other person was killed in the town of Quapaw in the north-east of Oklahoma where officials said many buildings were badly damaged.

Tornadoes also struck in Nebraska, Kansas, Iowa and Missouri.

President Barack Obama, on a trip to the Philippines, offered his deepest condolences to those affected and said federal emergency officials would be on the ground to help: "Your country will be there to help you recover and rebuild, as long as it takes."

'Mass casualty situation'

Most of the casualties were in suburbs west and north of Little Rock. The Arkansas Department of Emergency Management said 10 people died in Faulkner County, five in Pulaski County and one in White County.

Mayflower and Vilonia, two small towns in Faulkner County, appear to have borne the brunt of the damage. In Vilonia, the County Sheriff's office spoke of a "mass casualty situation".

The Arkansas tornado touched down about 10 miles (16km) west of the city of Little Rock and left a 40 mile (65km) path of destruction.

It is said to have passed through several northern suburbs - including Mayflower where a witness described a twister half a mile wide crossing Interstate 40 on Sunday evening, the National Weather Service said.

One tornado left a 40 mile (65km) trail of destruction

Many vehicles and buildings were wrecked in the town of Mayflower

Winds ripped through foundations blowing entire homes away

Congressman Tim Griffin told Reuters news agency an "entire neighbourhood of 50 homes or so" in Faulkner County had been destroyed, with many "completely gone except the foundation".

Many homes and businesses, including a new secondary school worth $14m (£8.3m), were left in ruins in Vilonia after the storm.

"There's just really nothing there anymore. We're probably going to have to start all over again," said Vilonia schools chief Frank Mitchell after inspecting the wreckage of the school.

First reports from Oklahoma said two people had died in Quapaw but officials later revised the figure down to one. Another six people were injured.

Quapaw, which has a population of about 900, was badly hit by the tornado, Ottawa County Emergency Management director Joe Dan Morgan said.

"Looks like about half of town got extensive damage as well as the fire department," he said.

The tornado then headed northwards into the state of Kansas where it struck Baxter Springs, injuring several people and causing further damage.

Over the weekend, storms struck the eastern part of the US, killing a child in North Carolina.

Buildings on Main Street in Quapaw were damaged

Baxter Springs, Kansas, was hit by the same tornado that struck Quapaw

Trees were ripped apart by the storm in Baxter Springs