Emergency officials say two people have died in tornadoes in Oklahoma, just two days after scores were killed in neighboring Missouri, in the deadliest tornado to hit the United States in nearly 60 years.
Officials say tornadoes on Tuesday injured several people. The extent of the damage is not yet known.
A National Weather Service statement warned residents in wide swaths of Oklahoma and Kansas to "take shelter" as a precaution both for the tornadoes and because of severe thunderstorms that had the conditions necessary to form more of them. Forecasters also were warning of baseball-sized hail and strong winds.
Severe thunderstorms also threatened Joplin, Missouri, where on Sunday a devastating tornado crushed cars, uprooted trees and ripped apart buildings. At least 122 people died in that storm, and more victims may be found as rescuers are still searching through the wreckage.
U.S. President Barack Obama says he will travel to the storm-devastated area on Sunday. Speaking during a visit to London Tuesday, Mr. Obama pledged that the federal government will use all available resources to help the victims recover and rebuild.
Weather officials say 481 people have now been killed in the country this year by tornadoes, the deadliest toll since the 519 recorded in 1953.
Last month, tornadoes and violent thunderstorms killed more than 300 people across the southern United States. Alabama bore the brunt of the fatalities, with more than 200 dead.