Deadly tornado ravages Missouri, 24 reported dead

The tornado struck the town of Joplin near the border with Oklahoma and Kansas less than a month after a horrific tornado outbreak left 354 dead across seven US states.

It was the deadliest of 46 tornadoes reported to the National Weather Service in seven states Sunday.

People clawed through the rubble looking for friends, family and neighbours after the late afternoon storm tore buildings apart and turned cars into crumpled heaps of metal.

Flames and thick black smoke poured out of the wreckage of completely unrecognizable homes and water gushed out of broke pipes as shocked survivors surveyed the damage, early photos showed.

A tangled medical helicopter lay in the rubble outside St. John Regional Medical Center, which took a direct hit.

Missouri Governor Jay Nixon declared a state of emergency and activated National Guard troops in response to what he described as "significant destruction in multiple areas, including Joplin, where a tornado struck St. John's Regional Medical Center."

The badly damaged medical center was evacuated Sunday and Nixon warned that the storms are not finished.

President Barack Obama sent his "deepest condolences" to victims and said the federal government stood ready to help Americans as needed.

On Saturday, a deadly tornado pummeled the east Kansas town of Reading, killing a man and damaging an estimated 80 percent of Reading's structures, mostly wood-frame buildings.

According to witnesses, it crushed a grain elevator, tore the top off the red brick post office, blew the back off the local fire department building, tore houses off foundations and uprooted trees.

A tornado was also responsible for the death of one person in Minneapolis, Minnesota, on Sunday, authorities said. At least 18 others in that city and its suburbs were injured.