Losses from the deadly burst of tornados that swept the US south and midwest late last month could hit as much as $7 billion, a company which estimates catastrophe damages said Monday.

Insured losses from the massive twister that killed a record 138 people in Joplin, Missouri, on May 22, and 150 other tornados that struck during May 20-27, are likely to run $4-7 billion, AIR Worldwide estimated.

The losses include residential, commercial, and industrial properties and their contents, and automobiles, Boston-based AIR said.

The late May storms were only a part of the most deadly and damaging tornado season in the country in 75 years, leaving a swathe of destruction across several states and 523 dead.

"It is also becoming quickly apparent that 2011 will surpass 2008 in terms of insured losses from severe thunderstorm activity. Indeed, the two major outbreaks of this year -- the first in late April, the second in late May -- are the costliest on record," AIR's principal scientist Tim Doggett said in a statement.

An outbreak of dozens of tornados killed 314 people in five states on April 27.

Twenty states suffered damage in the late May storms, AIR said.

"Thousands of buildings were damaged, hundreds more were completely destroyed, and more than a thousand people were injured," it said.