At least 89 people have been killed and hundreds injured after a tornado tore through the city of Joplin in the US state of Missouri, officials have said.
Joplin official Mark Rohr said the storm cut a path six miles (10km) long. Homes and businesses were flattened and a damaged hospital had to be evacuated.
Power lines are down and telephone connections are largely cut off.
The Governor of Missouri, Jay Nixon, has declared a state of emergency and warned that more storms are on the way.
Cities in three other Midwestern states have also been badly affected. At least one person was killed in Minneapolis, Minnesota.
Last month, tornadoes and storms killed at least 350 people in Alabama and six other southern states.
Jeff Lehr, a reporter for the Joplin Globe newspaper, said he was upstairs in his home when the storm hit the city of about 50,000 at about 1730 (2230 GMT) on Sunday but was able to make his way to his basement.
"There was a loud huffing noise, my windows started popping. I had to get downstairs, glass was flying. I opened a closet and pulled myself into it," he told the Associated Press.
"Then you could hear everything go. It tore the roof off my house, everybody's house. I came outside and there was nothing left."
Another resident, Tom Rogers, said his house had been destroyed.
"It's just gone. We heard the tornado sirens for the second time. All of a sudden, everything came crashing down on us. We pulled our heads up and there was nothing. It was gone," he told the Joplin Globe.
Much of the city's south side is reported to have been levelled, with churches, schools, businesses and homes reduced to rubble. Power and telephone lines across the city were also downed, and many vehicles overturned.
Nearly 100 patients at the St John Regional Medical Center in Joplin were having to be evacuated from after the hospital took a direct hit.
A resident living 45 miles (70km) away said debris from the hospital had landed in his yard, including medical supplies and X-rays.
At a pre-dawn news conference on Monday outside the St John Regional Medical Center, Mr Rohr announced that the number of confirmed dead was 89.
He said the tornado had cut a path nearly six miles long and more than half a mile (800m) wide through the city centre, and that tornado sirens had given residents about a 20-minute warning.
Fire chief Mitch Randles said the tornado "cut the city in half" and estimated that 25 to 30% was damaged.
A door-to-door search of the damaged area will begin later on Monday morning, but progress will be slow because of the danger of downed power lines and gas leaks, which caused fires around the city overnight.
"We will recover and come back stronger than we are today," Mr Rohr said.
Earlier, the Red Cross opened a shelter at Missouri Southern State University in Joplin for victims, spokeswoman Joanne Muir told the BBC.
It had also sent an emergency response vehicle with some supplies such as blankets, cots, water and food to the area, she said.
US President Barack Obama - on his way to the Republic of Ireland - sent his condolences to those affected.
"Michelle and I send our deepest condolences to the families of all those who lost their lives in the tornadoes and severe weather that struck Joplin, Missouri, as well as communities across the Midwest today," the president said in a statement.
"We commend the heroic efforts by those who have responded and who are working to help their friends and neighbours at this very difficult time."
Governor Nixon said storms had caused extensive damage across Missouri.
"They continue to pose significant risk to lives and property," he said in a statement.
"As a state, we are deploying every agency and resource available to keep Missouri families safe, search for the missing, provide emergency medical care, and begin to recover." he added.
He warned that the storms were not finished.
"I urge Missourians to keep a close eye on the latest weather information and to follow the instructions and warnings of emergency personnel as these deadly storms continue to move through our state," he said.