Tornadoes swept vehicles from the road near El Reno, Oklahoma Tornadoes sweeping the US Mid-West have struck near Oklahoma City, hitting vehicles on a section of motorway west of the Oklahoma state capital.
Official said at least four people had been killed and many others injured.
The new storms come as rescue workers search for hundreds of people missing in Joplin, Missouri, about 200 miles (320km) to the north-east.
At least 122 people were killed there on Sunday by a powerful tornado that cut a wide swathe through the city.
The Oklahoma tornadoes hit rural areas to the west and south of Oklahoma City, officials said.
State officials said at least four people had been killed.
The emergency director for Canadian County, Jerry Smith, said two people in his county had been killed, but he had no details on how they died.
He said a number of people were reported to have been injured after a powerful tornado struck a section of the highway in Canadian County, throwing cars off the road.
March 1925: Deadliest twister in US history as so-called Tri-State Tornado kills 695 in Missouri, southern Illinois and south-west IndianaMarch 1932: Deep South tornado outbreak kills 332 people from Texas to South Carolina, with 270 dying in Alabama aloneMay 1840: The Great Natchez Tornado kills 317 people in Mississippi town, most living on flatboats on the riverApril 1974: 310 killed in 24-hour “super outbreak” of 148 tornadoes across 13 states.May 1896: Two weeks of storms kill 305 people in Missouri, Illinois and Kentucky
A regional medical official said three children in the town of Piedmont, north-west of Oklahoma City, were badly injured.
At least one gas explosion was reported in the town of El Reno.
The tornadoes formed from storm systems that began in western Oklahoma state and began travelling north-east in the afternoon.
As the storms built up, Oklahoma Governor Mary Fallin warned people to take shelter.
“This is a very dangerous time right now,” she told CNN.
Television reports showed tornadoes forming and striking the ground.
The storms were forecast to move over Joplin, Missouri, bringing the possibility of more tornadoes for the badly-damaged city.
Rescue workers were combing through the wide path of debris Sunday’s twister left, hoping to find some of the hundreds of people still unaccounted for.
The huge tornado cut a path some six miles (10km) long and at least half a mile wide through Joplin.
Rescuer Keith Beck says crews are searching Joplin “street by street” in the hope of finding survivors
Much of the south side of Joplin is reported to have been levelled, with churches, schools, businesses and homes reduced to rubble.
US President Barack Obama said he would visit tornado-hit Missouri on Sunday, immediately after he returned from a six-day tour of Europe.
He called the Joplin tornado “devastating and heartbreaking” and promised the government would “do absolutely everything we can” to help victims recover and rebuild.
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