TOLEDO, Spain – At least 68 people are dead after two high-speed trains slammed into each other south of Madrid — and Spain's own transport minister says the decision that led to the carnage is "inexplicable."

More than 500 passengers were aboard the two trains when they collided between the towns of Mora and Orgaz, near Toledo, on Wednesday.

The toll, confirmed by regional president Emiliano García-Page, makes it Spain's deadliest rail disaster since 2013. Dozens more are still being treated for serious injuries, with makeshift medical tents and a sports complex in the village of Urda turned into emergency care centres.

Emergency crews work around the wrecked high-speed train carriages on a rocky embankment near Mora, south of Madrid
Emergency crews work around the wrecked carriages on the embankment near Mora, south of Madrid, on Wednesday. (Supplied)

COMPUTER MELTDOWN

Transport Minister Óscar Puente told reporters the accident was "truly unbelievable."

According to Puente, a computer failure forced six moving trains to a halt — including the two that would later crash.

In a system failure, he said, the control centre is supposed to take over. And that's exactly what it did: it cleared the trains to start moving again without any speed restrictions.

That call was made "under inexplicable circumstances."

The result was catastrophic. A Renfe train plowed straight into an Iryo service that was still standing on the tracks ahead.

Iryo confirmed its train was "struck from behind."

Rescuers in high-visibility gear work beside derailed train carriages under portable floodlights at dusk
Rescue teams search the derailed carriages under floodlights as darkness fell over the crash site. (Supplied)

'PEOPLE FLEW OFF THEIR SEATS'

Survivors described seconds of terror as the carriages buckled and overturned.

"We felt the train move, derail, and we were tilted," passenger Miguel Ángel Pérez told Spanish TV. "It was a terrible few seconds."

He said the carriage partially overturned, and travellers were cut by open tray tables.

Eduarda, who was on board with her two cats, was thrown forward so violently the table in front of her snapped. Once outside, she heard screaming and saw a carriage on fire — and bodies beneath the train.

Spanish journalist Roberto Gómez, who was travelling on one of the trains, called the scene "extremely chaotic and very distressing."

"Lives have been shattered, families have been torn apart, the pain is immense."

— Spanish PM Pedro Sánchez

SPAIN 'GRIEVING'

Prime Minister Pedro Sánchez rushed to the crash site and announced three days of mourning starting Thursday.

"Today Spain is grieving, the whole of Spain is grieving," he said. "Lives have been shattered, families have been torn apart, the pain is immense."

Behind every victim, he said, is "a destroyed family, pain and anguish."

Sánchez vowed to "get to the bottom of this," warning that "if there has been any negligence, it will come to light," and that any failures in the security system would be addressed.

He also acknowledged the unthinkable: a second high-speed horror on the same line in a single year. A crash earlier this year killed 48 people.

"At the moment it looks like the causes behind both crashes have nothing in common," he said, adding that investigators would decide. "It is unacceptable for a country like Spain to experience two high-speed rail accidents in the same year."

King Felipe called the disaster a "terrible tragedy."

Emergency responders line the tracks beside a white high-speed train lit by floodlights at night
Emergency workers comb the trackside beside the wrecked high-speed train overnight. (Supplied)

CAMPAIGNING HALTED

Most major political parties have suspended general election campaigning as the country comes to terms with the scale of the loss.

Emergency crews were still working through the wreckage late Wednesday, and authorities warned the death toll could rise further.