More than 600 witnesses and 107 experts have been called to testify in what prosecutors claim was an al Qaeda-inspired attack by radical Islamists in retribution for Spain's participation in the US-led interventions in Iraq and Afghanistan.

The trial gets underway amid ultra-tight security at the high court venue on the outskirts of Madrid, and is expected to last some six months.

Three men -- Rabei Ousmane Sayed Ahmed, a 35-year-old Egyptian; Hassan Al Haski, alias Abu Hamza, a 43-year-old Moroccan; and Youssef Belhadj, a Moroccan who had the alias "the Afghan" -- are said to have organized the bombings.

The four alleged masterminds spent a year planning the worst terror attack in Europe since the December 1988 bombing of a PanAm jet over the Scottish town of Lockerbie that killed 270 people.

Suspects face 40,000 years each in prison

The three bombers placed bags packed with some 10 kilogramms (22 pounds) of explosives on four commuter trains during the busy morning rush hour, then left and activated the devices by mobile telephone.

One of the four alleged masterminds of the coordinated bombings of four packed Madrid commuter trains on March 11, 2004, Rabei Ousmane Sayed Ahmed, alias "Mohammed the Egyptian," was expected to be the first called to testify.

He is one of seven men facing sentences of some 40,000 years each for the deaths and membership in a terrorist organisation, although under Spanish law the longest jail term anyone can actually serve is 40 years. The others accused will stand trial for lesser offences, including collaboration with a terrorist group and falsifying documents.

All those on trial will give evidence from a bullet-proof box at the venue. Media, survivors and relatives of the victims will be able to watch via closed circuit television in different rooms, although a handful of seats in the 180-seat courtroom have been reserved for the public.

Survivors still struggling to heal scars

In addition to the 191 people killed in the bombings, another 1,824 people were wounded. Many of the survivors are struggling to heal both the physical and psychological scars inflicted by the tragedy.

"We want to understand how they were able to toy with our lives as they did," said Eloy Moran who was on one of the four suburban trains blown up on March 11, 2004. "I hope eventually to be able to throw off the label of victim," said the man who lost sight in his left eye and hearing in his left ear.

It was a Thursday morning just before 7:40 a.m., and Moran had just folded his newspaper to prepare to get off the train.

"There were just three minutes to go and I was calm," he recalled. "The train then stopped and there was a brutal explosion just in front of me. I received a big blow on the head. I felt my head was expanding, I thought it would explode, like it was the end for me."

After that, there was only silence and darkness, he said.

"I checked myself over to see I was in one piece but I couldn't get up. Everything around me had been destroyed."

Looking for closure

Angeles Dominguez, now 53, was on the same train. She has only just returned to work after the reconstruction of her eardrums which were perforated in the blast.

She was caught in the shockwave of the first bomb, several carriages in front of her sixth carriage. But she has no recollection of the three other bombs that hit the same train, one of which went off near the seat she had been sitting on. She suffered seven broken ribs and retains only 40 percent of her hearing.

The trial "will allow us to put names and faces to those who are to blame" and "let us finally to turn the page," said Dominguez, who heads a victim support organization.

As with every commemoration, television and the newspapers are going to show the images again and that's very tough for the victims to bear," said Dominguez.

But she believes the trial will be a necessary stage of closure for the survivors and those who still mourn dead relatives.

Survivors critical of investigation

Moran and Dominguez share the concerns of many survivors who believe -- ahead of a trial expected to last six months and involve 600 witnesses -- that the investigation was not exhaustive enough.

Of the 29 defendants, seven each face some 40,000 years in jail with the prosecution having identified six as the chief plotters of the worst militant attack in Spain.

Dominguez said he hopes the trial of the bombers and plotters and some of their leading associates "will perhaps allow us to obtain responses to many questions."

Pilar Manjon, who heads another victims association, says that she wants to see "justice done" in order "one day to be able to rebuild" her life.

She lost her son in the blasts and became renowned in Spain when on Dec. 15, 2004, she made an emotional appearance before a parliamentary commission of inquiry into the bombings, accusing politicians of putting party quarrels above the victims.

Physical and psychological scars

Moran and Dominguez realize that after spending a short period in hospital they were among the lucky ones from that terrible day. Many of the wounded lost arms or legs, and the psychological scars run deep for all.

Moran has never been able to go back on a train. Nor has he returned to work as a civil servant.

"I still have problems concentrating and sleeping," he explained. "It makes me sad to think that March 10, 2004, was my last day at work. I loved my job."

Dominguez said she was able to find a positive side to the tragedy.

"Life can still bring new opportunities," she insisted, having made many friends among the 500 or so victims affiliated to her association.