Tornado 265 km per hour struck a city of Missouri State, causing the heaviest losses.

This left more than 120 people dead and over 750 wounded and hundreds of others unaccounted for as of May 25.

The economic losses are estimated to be 3 billion U.S. dollars at maximum.

Foreign press reports said that buildings in the city were almost leveled, reducing it to debris.

Tornados also hit Oklahoma, Arkansas and other states on May 24 and 25, killing 15 persons and wounding at least 60 and leaving their population without power supply.

This put the death toll by tornadoes in the U.S. up to now at more than 500 people.

April alone witnessed 875 tornados, the worst month in its history.

It is expected that more tornados will hit the U.S. in the days ahead.

Experts said that the frequent tornados in the U.S. are attributable to La Nina phenomenon in which the temperature of the water in the East Pacific periodically goes down.