The victims were an elderly British couple on holiday in the small town of Finestrat on Spain's Mediterranean coast.
Heavy rainfall in the mountains above the town caused a nearby river to burst its banks Friday, sending a torrent of water rushing through a normally-dry channel used as a marketplace.
Stalls and cars were swept away by the rushing water. Bystanders said the pair were knocked off their feet and became trapped underneath a vehicle.
The flood came as a surprise to marketgoers, eyewitnesses said, since it was not raining in Finestrat itself at the time.
The incident comes just a day after flooding killed one person and caused traffic chaos in Rome, Italy.
With files from the Associated Press