France has been battered by heavy rain since Storm Alex made landfall on Thursday afternoon.
Three rescue workers died on Sunday night when their helicopter crashed for unknown reasons as they took part in emergency assistance missions over south-east France, where torrential rainfall and flooding caused the deaths by drowning of three other people.
Interior minister Christophe Castaner travelled to the Var region to meet victims and rescue workers as rain continued to fall in the region.
At least 10 people are reported to have died in flash flooding in the Languedoc region of southern France where very heavy rainfall fell for an unusually long period overnight Sunday, with waters reaching a high of seven metres in some places.
Officials say a 70-year-old German man who was helping to supervise children at one of the summer camps hit by the floods is missing.
Heavy rainfall is now threatening several French regions with flooding, including the French capital and outlying areas as the River Seine is forecast to reach or surpass the level that incurred serious damage in June 2016.
French Prime Minister Manuel Valls said that the full cost of week-long floods is still unclear and pledged a special fund for those worst-hit.
Red flood alerts were eased on Sunday as clean-up operations began in parts of north and central France with damage to rail network described as 'catastrophic'.
Several towns were under water Thursday, while Paris museums and a metro line were forced to close as forecasts were for continuing rain this weekend.
The floods have hit towns and villages from the north-central loiret region to the Channel coast, while in Paris the river Seine has spilled over its banks.
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President François Hollande visited the region and expressed the 'solidarity of the nation' to those affected by the flooding tragedy.
Death toll could rise to 19 after violent storms sent water cascading through Antibes, Cannes and Nice.
Days of heavy rainfall followed by violent storms have caused flash flooding, with the southern Var département (county) hit worst.