Another five people were injured in the collision on a country road near Puisseguin in the Gironde region about 60km east of Bordeaux, an official from the local prefect’s office said.
A spokesman for the interior ministry said that, as far as he could tell, all the passengers were French and from the region.
President Francois Hollande, speaking on a visit to Athens, said he had been “plunged into sadness by the tragedy”.
The bus was carrying about 50 day-trippers south to the Landes region from their home in the village of Petit Palais just a few kilometres away from the crash side, officials said.
Most of them were elderly, the member of parliament for the Gironde region, Gilles Savary, told BFM TV.
