A tornado that spun across the Oklahoma-Missouri border in the United States has killed at least 22 people as severe storms raked the nation's heart, injuring many and mangling buildings in the storm-weary region.

Searchers are going through rubble looking for more victims and survivors.

The twister caught some local residents off guard.

"The sun was out and all of a sudden (the wind) picked up probably about 70 miles. The next thing I knew, there's all the debris and shingles from my house."

President George W. Bush sent condolence to the victims and their families earlier on Sunday, saying "Mother's day is a sad day for those who lost their lives in Oklahoma, Missouri and Georgia because of the tornadoes."

The twister was the deadliest in Oklahoma since a May 3, 1999 twister killing 44 people in the Oklahoma City area.