French Prime Minister Francois Fillon called the storm a "national disaster" after holding an emergency cabinet meeting coordinating rescue efforts in the wake of the storm.
French Interior Minister Brice Hortfeux said hundreds of soldiers and thousands of firefighters have been mobilized to help residents in the western districts besieged by floods with drainage operations.
French state meteorologists have warned that Xynthia was the strongest storm since 1999, when 90 people died. The state meteorology broadcaster maintained two departments, Finistere and Morbihan, on orange alert in its latest statement late Sunday as they were still threatened by uprising floods.
Moving to the northeast of Europe, the fierce storm killed one man in southern Belgium and brought down some electricity lines.
According to German official data, four people were killed in Germany as their cars were struck by trees dragged down by the gust. The Frankfurt airport had to cancel at least 200 flights due to sweeping winds up to 130 km per hour and the city's central train station was forced to close temporarily.
A woman in England was reportedly killed in her car by surging floods.
Before landing on France, Xynthia had already caused three deaths in Spain and one in Portugal.
