High winds battering northern Spain have brought down the roof of a sports hall near Barcelona, killing three children, local officials say, BBC reported.
Two adults died in other storm-related incidents elsewhere in the north.
Torrential rains and winds of up to 172km/h (107mph) have been battering northern Spain and south-west France.
At least one million homes in France are without electricity, roads and railways have been blocked and airports ordered closed, authorities there said.
Residents in affected areas in both countries have been warned to stay indoors.
French weather agencies forecast the storm but it has affected a wider area than expected. A state of "red alert" has been declared in nine departments.
Huge waves swept in from the Atlantic overnight battering the French and Spanish coastline.
In France, the storm has caused havoc from the Dordogne area to the Pyrenees.
As it moved east, the torrential rains caused flooding in some areas prompting thousands of calls to the emergency services.
The force of the storm also led to the closure of airports in Bordeaux, Pau and Biarritz, and Toulouse.
Train services have also ground to a halt, leaving several hundred passengers stranded in stations overnight.
The sports hall collapse happened in the town of Sant Boi de Llobregat, near Barcelona.
"Part of the building collapsed, there were between 20 and 30 youngsters inside. We know there are some dead and 16 injured," a local government spokeswoman told AFP news agency.
Two other deaths have been reported in Spain.
A policeman was killed by a falling tree as he directed traffic in Burela, Galicia, and a woman was killed by a wall collapse, reportedly in Barcelona.