Raging flood waters swept through the town of Letur in the eastern province of Albacete, pushing cars through the streets, images broadcast on Spanish television showed.

Emergency services workers backed by drones were looking for six people who were missing in the wake of flash floods in the town, the central government's representative in the Castilla- La Mancha told Spanish public television TVE.

"The priority is to find these people," she added.

Police in the town of L'Alcudia in the eastern region of Valencia said they were looking for a truck driver who has been missing since early afternoon.

"I am closely following with concern the reports on missing persons and the damage caused by the storm in recent hours," Prime Minister Pedro Sanchez wrote on X, urging people to follow the advice of the authorities.

"Be very careful and avoid unnecessary trips," he added.

Twelve flights which were due to land at Valencia airport have been diverted to other cities in Spain due to the heavy rain and strong winds, Spanish airport operator Aena said.

Another 10 flights which were due to depart or arrive at the airport were cancelled.

National rail infrastructure operator ADIF said it had suspended high-speed trains between Madrid and the eastern port of Valencia due to the effects of the storm on main points of the rail network" in the Valencia region until "at least" 10 am on Wednesday.

A high-speed train with 276 passengers derailed in the southern region of Andalusia, although no one was injured, the regional government said in a statement.

Emergency services rescued scores of people in Alora in Andalusia, some by helicopter, after a river overflowed.

State weather agency AEMET declared a red alert in the Valencia region and the second-highest level of alert in parts of Andalusia. Several roads were cut in both regions due to flooding.

Scientists warn that extreme weather such as heatwaves and storms is becoming more intense as a result of climate change.