Amateur footage of tornado in McAlester, Oklahoma
Tornadoes and severe storms have swept across the central part of the United States, causing destruction and killing at least 22 people.
A tornado severely damaged the north-eastern Oklahoma town of Picher before hitting the Missouri town of Seneca 15 miles (24km) away.
At least six people died in Picher, 15 in Missouri and one in Georgia.
An emergencies official in Picher said a 24-street area of the town had been "virtually destroyed".
Michelann Ooten warned that the death toll could climb as rescuers sifted through the rubble looking for survivors.
Television images showed overturned cars, homes ripped from their foundations and trees stripped of their leaves.
'Thoughts and prayers'
Oklahoma Governor Brad Henry has ordered National Guard troops to arrive in Picher by Sunday morning to help in rescue and recovery operations, Ms Ooten added.
At least three of the people killed in Missouri died in Seneca.
"The last two years we've had floods and tornadoes - it's just one right after another," said Susie Stonner of the State Emergency Management Agency.
Mr Henry, who plans to visit the area later on Sunday, said a major emergency response was under way.
"Our thoughts and prayers are with the people of Picher and all of the other Oklahoma communities that have been impacted by the latest wave of severe weather," he said.