Floods in Germany and France have killed at least 10 people and forced thousands from their homes, officials said Thursday as Paris' Louvre museum announced it would move treasures out of reach of the swollen Seine.

The world's most visited museum said it would shut its doors Friday to evacuate artworks from its basement storage, as the nearby river began to burst its banks following days of torrential rain.

Several towns in southern Germany have been devastated by flooding that has also seen rescuers in central France rowing lifeboats down streets turned into muddy rivers.

Forecasters in both countries warned of more downpours over the next 24 hours.

In France, a man on horseback died after he was swept away in a swollen river in Evry-Gregy-sur-Yerre, southeast of Paris, the local prefecture said.

The 74-year-old's body was recovered from the water by firefighters. The horse made its own way back to safety, police said.

There were also chaotic scenes in the German town of Simbach am Inn, where the force of the water swept away the entire stock of a sawmill, leaving huge stacks of splintered wood blocking roads.

On one street, a car could be seen parked vertically against the wall of a house, pushed there by the floodwaters. Many other vehicles lay flipped over on roads blanketed by mud.

Five people have been killed in the Simbach area, including three women from the same family -- a mother, grandmother and daughter -- who had been trapped in their house.

Two other elderly people were also found dead in their homes.

"The (rise in) water was so quick that practically no residents had the time to run away," police spokesman Armin Angloher said.

The deaths bring the toll from the floods in Germany to nine, including four killed earlier this week in the southern region of Baden-Wuerttemberg.

Three others are missing, a police spokesman in Bavaria state said.

German Chancellor Angela Merkel said her thoughts were with the families "who have been plunged into this devastation".

- Paris museums on alert -

Some towns in central France have been hit by their worst floods in over a century, with more than 5,000 people evacuated since the weekend and around 19,000 homes without power.

In Paris, officials were erecting emergency flood barriers along the Seine. The riverbanks are home to both the Louvre and the Orsay museum, which was also preparing for the worst.

The Orsay, a converted railway station which hosts the world's greatest Impressionist collection, closed early Thursday and was to move its most vulnerable works to upper floors if the Seine rises more than 5.5 metres (18 feet).

While the river's swelling has so far caused little damage in Paris and is unlikely to submerge the city centre, it is set by some estimates to rise as high as six metres above its usual level by Friday.

"It's amazing. I have been here many times and it's the first time I have seen the river so high," said Brian Alan, an American tourist from Atlanta, Georgia, who was watching the scene from the Alexander III bridge.

Rescuers in the Parisian suburb of Longjumeau were paddling up streets in lifeboats, while in the town of Montargis, only the tops of cars could be seen peeking above the surface.

About 200 people had to spend the night in a gymnasium in Nemours south of Paris and Prime Minister Manuel Valls, visiting the flooded town's a crisis control centre, said at least 2,000 more people needed to be evacuated.

"The situation remains tense and difficult," he said.

- 'Catastrophe' -

French President Francois Hollande said a state of "natural catastrophe" would be declared when the cabinet meets next Wednesday.

The rains have hit the French Open tennis tournament, washing out play earlier in the week and leaving players facing a heavy match schedule ahead of the finals.

Schools and roads have also been flooded in Austria in recent days, though the waters have now receded.

Heavy rains have also been lashing the Netherlands, with more bad weather expected. Television images showed streets in the southern towns of Boxmeer and Deurne already ankle-deep in water.

burs/kjl/mfp