It was a huge shock for Spain, which had experienced decades of violence at the hands of the Basque separatist group ETA but had never been hit by an Islamist attack of such magnitude.

10 blasts in quick succession

At the main Atocha station in the city centre, which lies close to the Prado Museum, three almost simultaneous explosions ripped apart a train that just arrived from Alcalá de Henares, a Madrid suburb, at 7:37 am.

Hundreds of passengers were hurled to the floor or against the walls of the carriages by the blast, with bloody victims crawling from mangled wreckages as other panicked commuters on the platform fled to the escalators in a cloud of smoke.

In the minutes that followed, seven more bombs exploded on three other trains that had also left Alcalá de Henares — one which was waiting to enter Atocha, and two others at El Pozo and Santa Eugenia, both nearby stations.

In one of Atocha’s huge halls, forensic pathologists worked to identify victims as taxis helped ambulances ferry the injured to hospital.

Some victims wandered through the city in a state of shock for several hours before getting medical attention.

ETA wrongly accused

Several hours later, the right-wing Popular Party (PP) government of prime minister José María Aznar publicly blamed ETA which had carried out dozens of deadly attacks over the past decades.

Several specialists raised the possibility that the attacks may have been orchestrated by Islamic extremists but the idea was dismissed by the interior minister as “misleading”.

At the time, Spain was in the final days of campaigning ahead of the March 14th election with the country deeply divided over the government’s decision to join the US-led war in Iraq which began the previous year.

But doubt was soon cast on the ETA hypothesis when hours after the attacks, investigators found a stolen minivan in Alcala de Henares that contained seven detonators and a tape of Koranic verses.

Two days later, a videotape was found in a bin near Madrid’s main mosque with a message claiming responsibility for attacks in the name of “Al-Qaeda in Europe” as punishment for Spain’s involvement in the Iraq war.

Right loses election

The shock caused by the attacks — the deadliest ever on Spanish soil — weakened the PP which came under fire for insisting ETA was to blame despite mounting evidence to the contrary.

On March 12th, some 11.6 million people joined massive nationwide demonstrations in protest at the attacks, with many chanting slogans expressing doubt over the government’s version of events.

The PP was defeated in the election by José Luis Zapatero’s Socialists, who promptly withdrew Spain’s troops from Iraq once he was sworn in as prime minister.

For years after the attacks, top PP officials continued to cast doubt on the Islamist nature of the bombings, helping to fuel conspiracy theories.

18 convicted, only 3 left in jail

Three weeks after the bombings, seven suspected members of the cell involved in the carnage blew themselves up in an apartment where they had been hiding in Leganes on the southwestern outskirts of Madrid.

After a three-year investigation, 29 other suspects went on trial in early 2007. Most were Moroccan nationals who were living in a working-class neighbourhood of Madrid but there were also several Spaniards, a Syrian and an Egyptian.

At the end of the six-month trial, 18 men were convicted.

Three of them — Jamal Zougam, Othman el Gnaoui and José Emilio Suárez Trashorras — received vast, symbolic sentences of over 30,000 years in prison. Only these three remain in jail.