The class-action suit filed in federal court seeks to represent all Hurricane Katrina victims in Louisiana. Named as defendants are Exxon Mobil Corp., Chevron, Shell Oil, BP, and several exploration and pipeline companies.

It alleges "that the major oil companies' oil, gas and pipeline exploration and drilling activities throughout southeast Louisiana resulted in ecological damages to such an extent that coastal marshes were destroyed which previously had protected New Orleans naturally from Katrina level hurricane force winds and tidal surges," the lawyers said in a statement.

"Everyone has been talking about the failures of the state, local and federal governments in the wake of Hurricane Katrina," said Val Exnicios, one of the lawyers in the case.

"We believe it's the right time to pinpoint who's essentially responsible for the devastation caused by Katrina in the first place -- the major oil and gas companies, who haphazardly dredged thousands of miles of exploration and drill site canals throughout south Louisiana to extract oil and gas."

The lawsuit alleges that some 400,000 hectares (one million acres) of marshlands in southeast Louisiana disappeared as a result of the companies' oil and gas activities.

It noted that before the 1930s and 1940s when oil firms began dredging, the coastal marshlands provided a natural barrier of some 160 kilometersmiles) between the Gulf of Mexico and the City of New Orleans.

"Their years of negligence and callous indifference to the marshland ecology led to Katrina's disastrous consequence," the lawyer said.

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