At least 11 adults were killed in separate incidents in Spain and France as gales buffeted the region for a second day, cutting power, disrupting flights and blocking roads. Forest fires, one caused by felled power lines, raged in Spain.
In the sports centre disaster, winds of more than 100 km (62 miles) per hour, ripped the metal roof off a building next to a baseball court in Sant Boi, causing the breeze block walls to collapse inwards.
"It was horrific," Jose Antonio Godina, a parent, was quoted as saying by El Mundo newspaper.
"We heard a loud noise and we thought a tree had fallen on a roof. But when we got here, the roof of the annexe had literally flown off and the walls had fallen in on them."
Four children, members of a junior baseball team, were killed, local authorities said. Nine people were injured, including seven children.
A policeman was killed by a falling tree in Galicia, northern Spain on Saturday, a police spokesman said, while a 52-year-old woman was killed when a wall collapsed on her as she walked down a street in Barcelona on Friday.
A 51-year-old man was killed by a falling wall in Alicante, authorities said, while two more adults were killed by falling trees in Catalonia on Saturday. A Portuguese captain died after being rescued from a ship in high seas off the coast of Galicia.
A 73-year-old woman was killed when a door blew on top of her in the northern province of Burgos, local authorities said.
The Spanish army stepped in to help fight a forest fire in La Nucia, north of Benidorm in Alicante, started by an electricity pylon felled by gales, the Ministry of Defence said. Thousands were evacuated from nearby housing estates.
Forest fires also raged in the region of Catalonia, putting emergency services on high alert, authorities said.
In France, gales cut power supplies to around 1.7 million homes and closed roads, railways and airports.
Local authorities in the Landes area said a 50-year-old man was killed when a tree fell on a car. A 78-year-old man died in his garden when he was hit by a piece of debris. The body of a third victim, a 75-year-old man, was found crushed by a tree.
Later, French state television reported that an elderly lady died when her respiratory support machine failed because of a power cut caused by the storm.
Tens of thousands in Spain were left without power and gales disrupted flights and rail travel. Waves of more than 20 metres (65 feet) were registered off the northern coast and high winds stranded dolphins on beaches in the region.
Winds of up to 190 km an hour paralysed southwest France. The French weather agency Meteo France placed the region on red alert and asked residents to stay indoors for their own safety.
French Agriculture Minister Michel Barnier said the storm was the worst since 1999, when a huge storm killed 88 people, and said France would call on the European Union to help fund reconstruction efforts.
President Nicolas Sarkozy told reporters he would travel to the affected area on Sunday.
Interior Minister Michele Alliot-Marie said she had ordered 700 extra security forces to be sent to help with rescue efforts and that extra equipment would also be sent to help clear roads and electric lines.
The airports at Bordeaux, Biarritz and Pau were closed.
The national power grid manager, Electricite Reseau Distribution France (EDF), said it could take a long time to restore power.
The French state railway company SNCF said it had been forced to halt services completely in the Aquitaine and Midi-Pyrenees regions, and asked travellers to postpone their journeys. It said high-speed TGV trains from Bordeaux had been stopped because of an electrical fault caused by the storm.