Rescue crews in the United States are searching through rubble for survivors a day after tornadoes tore three states, killing at least 22 people and shattering homes and businesses.

US President George Bush called it a sad day for devastated communities in the states of Missouri, Oklahoma and Georgia, and promised emergency federal aid.

Missouri's department of emergency management said 14 people were confirmed dead in the state, with scores more injured.

Numerous tornadoes touched down in Oklahoma late Saturday as the storms ripped across the state at speeds between 55 and 70 kilometres an hour.

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