Oklahoma City struck as tornadoes sweep US Mid-West
Tornadoes sweeping the US Mid-West have struck near Oklahoma City, hitting vehicles on a section of motorway west of the Oklahoma state capital.
Officials said at least 13 people in three states were killed.
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.
At least four major tornadoes hit rural areas of Oklahoma to the west and south of Oklahoma City, killing five, officials said. Twisters also killed three in Arkansas and two more in Kansas.
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.
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.
A weather-monitoring site in El Reno recorded winds of 151mph (243km/h).
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.
Two more people are reported to have died in Kansas in storms there on Tuesday.
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.
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.