More than 1,000 people demonstrated outside the transport ministry in Madrid on Wednesday after two trains travelling to Seville from the capital crashed that morning. The driver had been wrongly informed that the track was clear.

It was the second mass casualty train crash in Spain this year, after 46 people were killed in Adamuz in January, and comes ahead of elections next month.

Wednesday’s protests, called by hard-Right groups, were dispersed by riot police with baton charges and tear gas after objects were hurled.

It was the latest sign of growing unrest in Spain, with Barcelona and Bilbao also the scene of protests over the past week.

Protesters clash with police in Madrid Wednesday’s train crash in Urda, south of Toledo, was Europe’s deadliest train accident since 2013.

Rescue workers are continuing to search for human remains among the wreckage and 57 people remain in hospital.

Search teams with sniffer dogs and cranes shifted the carriages as police and soldiers picked through the wreckage strewn down the gravel slope where at least three train carriages were tossed by the impact. Testimonies of survivors filled Spanish television for a second day.

Pablo López, who was on the train that was hit from behind, recounted the moment of impact and the horrific aftermath to state broadcaster TVE.

“The image I have in my head is of a person crawling on the ground after being shot out of the other train,” he said.

Tars flow at the minute’s silence at the Atocha railway station for victims of the crash An outage of the electronic traffic control system on a stretch of line between Madrid and Seville had caused all trains in the area to halt.

Audio recordings show that rail traffic operators told the driver of one train to proceed at full speed despite the driver of another train, 15 miles ahead on the same southbound track, reporting that she could not restart connection with the system.

The Renfe AVE smashed into the back of the halted train, operated by the Italian company Iryo, causing carriages from both to be crushed and tumble down embankments on both sides of the line.

The high-speed rail network is considered one of Spain’s crowning achievements. It is the world’s second-largest, after China’s.

Óscar Puente, the transport minister, who has been under pressure since the Adamuz collision, said it was an “inexplicable” human error.

The socialist Mr Sánchez – who polls suggest is heading for defeat next month after eight years as prime minister – said an investigation would “get to the bottom of any possible negligence”. He said two crashes in one year was “unacceptable”.

The Adamuz incident revealed shortcomings in the high-speed rail infrastructure and led to months of cancelled services and speed restrictions while the track was updated.

Spain’s opposition parties have also pointed to the government’s corruption scandals, one of which saw José Luis Ábalos, the former transport and infrastructure minister, jailed for 24 years earlier this year.

Mr Sánchez was already under fire for the Ceuta migrant crisis, which saw tens of thousands of Moroccans flooding into the Spanish exclave in July.

Alberto Núñez Feijóo, who aspires to replace Mr Sánchez by leading the conservative People’s Party to victory next month, promised a complete audit of the railway system to uncover whether all budgeted spending on safety and maintenance had been properly used.

“Spain has the right to know what is happening with its infrastructures,” he said. “Every euro must be accounted for, what was announced and what was actually disbursed.”

“Corruption kills,” was the blunt assertion made by Santiago Abascal, leader of the far-Right Vox, which is set to hold the key to Mr Feijóo forming a majority. Mr Abascal called Mr Sánchez’s government “a criminal mafia that is responsible for these tragedies”.