Adding to the toll, a 53-year-old man who was trapped in his collapsed home in Harveyville, Kansas, was removed from life support at hospital and died, state officials said on Thursday.

President Barack Obama spoke with the governors of the storm-hit states Missouri, Illinois, Kentucky, Indiana, Tennessee and Kansas to offer condolences and help, the White House said. It was not immediately clear what assistance Obama offered, but it is typical for states to apply for federal disaster funding after damaging storms and other disasters.

Illinois Governor Pat Quinn asked for federal help to assess the damage to the southern third of his state, a precursor to formally requesting federal aid.

Six people died in Harrisburg, Illinois, the worst loss of life from the line of "super-cell" storms that marched across the Midwest and produced 35 tornado reports from late Tuesday through Wednesday.

A powerful tornado virtually demolished a Harrisburg residential neighbourhood and shopping district. Another 100 people were injured in the Illinois city, authorities said.

The tornado that struck Harrisburg was rated an EF-4 by the National Weather Service, one notch below the strongest category and capable of levelling buildings.

Another nine people in Kansas suffered storm-related injuries that required hospital care, state emergency management spokeswoman Sharon Watson said.

Power company crews were out on Thursday restoring electricity, and several residents sifted through rubble for something to salvage. Occasionally, a chain-saw roared to life, breaking the quiet.

The storms were also blamed for three deaths in Missouri, and three others in Tennessee as the violent weather moved eastward, officials said.

The body of Josephine Pavone, 62, one of three Tennessee storm victims, was recovered by rescuers who had to rappel down a hillside to free her from the ruins of her home that had been blown halfway down a ravine.

Friday could bring more rough weather, forecasters said.

"Tomorrow looks like it's going to be another bad day for severe weather. All the parameters are coming together - humidity, wind shear, a very strong jet stream," said AccuWeather.com meteorologist Henry Margusity.

He predicted multiple lines of thunderstorms crossing Indiana, Ohio, Kentucky and Tennessee - with several densely populated areas in the storms' likely path Friday evening.

Kentucky emergency management spokesman Buddy Rogers said officials will meet with National Weather Service forecasters to "get a feel for what could happen tomorrow."

This week's deadly storm outbreak raised concerns that this year could see a repeat of 2011, when 550 people were killed by twisters, the most in nearly a century.

(Reporting By Jim Young, Bruce Olson, Tim Ghianni; Writing by Andrew Stern; Editing by Paul Thomasch and Todd Eastham)

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