At least 51 people are known to have died after torrential rain caused devastating flash floods in southeastern Spain.

More than a year's worth of rain fell in just eight hours in the town of Chiva, near Valencia, and local officials say it is “impossible” to give a definitive death toll.

Footage uploaded to social media shows flooding causing chaos across the region, collapsing bridges and dragging cars through the streets. Another video appears to show people clinging to trees to avoid being washed away.

Large parts of the country were hit hard by heavy rains and hailstorms, causing rapid flooding in several areas.

More than 1,000 soldiers are deployed to help with the rescue operation as scores of people remain missing.

Local media also reported damage and victims in the Balearic Islands.

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Radio and television stations reportedly received hundreds of calls for help from people trapped in flooded areas or searching for relatives, as emergency services found it difficult to reach some areas.

Rescuers are using drones to search for missing people in the hard-hit municipality of Letur, local official Milagros Tolon told Spanish public television channel TVE.

“The priority is to find these people,” she said.

The city of Chiva was one of the first to feel the violence of the flash floods. Local media reported that by 6:00 p.m. (1700 GMT) on Tuesday, the city's streets had turned into rivers, with cars, streetlights and benches swept away by the force of the water.

It was only over two hours later that civil protection sent a warning to the residents of the Valencia region.

Many are now questioning the timing of that warning, saying it came too late for people to leave the streets or seek refuge in the upper floors of their homes.

Spain's Defense Minister Margarita Robles told reporters the flooding in the region was “an unprecedented phenomenon.”

She added: “Rescue services were on site yesterday night, but the avalanche of water was huge.”

Police have set up an emergency hotline and asked people to call 9006 5112 to report missing people.

“Practically all the main roads and also the side streets were closed,” said a government representative in the region, Pilar Bernabe.

“Not going out is not just a recommendation, but a necessity to ensure the safety of those stranded and those who need to rescue others.”

“If (the emergency services) have not arrived, it is not because of a lack of resources, but because of an access problem,” Valenica regional director Carlos Mazon said at a news conference, adding that it was “absolutely impossible” to access certain areas to reach.

Spanish weather service AEMET reported that Chiva in the Valencia region recorded 491 mm of rain in just eight hours on Tuesday – the equivalent of a whole year's worth of rain.

Red alert has been declared in the Valencia region and the second highest alert level has been declared in parts of Andalusia.

The floods have caused traffic disruptions as several flights were diverted to other cities and others canceled due to land traffic in Valencia. All train traffic in the Valencia region has been suspended, the national rail infrastructure operator ADIF said.

Valencia City Hall said all schools and sporting events were closed Wednesday and parks remain closed.

Many factors contribute to flooding, but warming of the atmosphere caused by climate change increases the likelihood of extreme rainfall.

The world has already warmed by about 1.1°C since the beginning of the industrial era, and temperatures will continue to rise unless governments around the world make drastic emissions cuts.

Additional reporting from BBC Weather's Matt Taylor.