Washington: At least 202 people were killed in tornado, which wiped out entire towns across six southern American states, said officials.

The vast majority of fatalities occurred in Alabama, where as many as 149 people perished, although Governor Robert Bentley said there were 131 confirmed deaths.

 A breakdown provided by Bentley’s office showed that violent weather claimed lives in 16 Alabama counties. Thirty people perished in DeKalb County in northeastern Alabama; the death toll in the hard-hit city of Tuscaloosa, in west-central Alabama, was at 36 as of Thursday morning, said Mayor Walter Maddox.

Mississippi emergency management officials also added 14 previously unreported fatalities to the count, increasing the death toll in that state to 32, officials said. At least one person died in both Arkansas and Tennessee and 11 died in Georgia. Virginia Governor Bob McDonnell said eight people were dead in his state.

Dave Imy, a meteorologist with the National Weather Service’s Storm Prediction Centre said the number of deaths was the most in a tornado outbreak since 1974, when 315 people died.

Entire neighborhoods were leveled and hundreds of thousands of people were without power, CNN reported. Bentley estimated as many as half a million to a million people were without power statewide.

Long before the death toll mushroomed, governors in Alabama, Mississippi and Georgia had declared states of emergency within their borders. Virginia also followed suit.

US President Barack Obama announced that he had approved Bentley’s request for emergency federal assistance, including search and rescue support.

“While we may not know the extent of the damage for days, we will continue to monitor these severe storms across the country and stand ready to continue to help the people of Alabama and all citizens affected by these storms,” Obama said in a statement.

This could be one of the most devastating tornado outbreaks in the nation’s history by the time it’s over,” CNN Meteorologist Sean Morris said.