Spain unveiled a towering monument on Sunday to those killed three years ago in the bombings that ripped apart rush-hour commuter trains — a glass oval containing messages of condolence written in the aftermath of Europe's worst Islamic terror attack.

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King Juan Carlos, Queen Sofia, senior government officials and an invitation-only crowd of several hundred people observed three minutes of silence at a solemn anniversary ceremony in memory of the 191 people killed and more than 1,800 wounded in the attacks of March 11, 2004.

Under glorious sunshine, a lone cellist played the mournful strains of "Song of the Birds" by Pablo Casals, a composition meant to be a call for peace. There were no speeches.

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Some in the crowd wiped away tears at the ceremony outside Atocha rail station, one of four targets in the string of 10 backpack bombs that struck morning rush-hour commuter trains.

Accompanied by guards wearing old-style plumed helmets, the king placed a laurel wreath at the foot of the monument: a 35-foot-tall glass cylinder with a transparent inner membrane bearing messages of condolence that Spaniards and other people left at Atocha after the attacks — on notes left at makeshift memorials of flowers and candles, or on a computer terminal set up for them to record their thoughts.

These messages, in Spanish and other languages, are only visible from an underground viewing chamber beneath the hollow, slightly oval-shaped monument.

"We are still here and we do not forget. Together forever," one message in Spanish reads. Another, in English, said, "Words are not enough."

The monument's designers say different phrases will stand out more clearly over the course of a day as the light shifts. At night, they are illuminated.

The Spanish monument's construction moved considerably more quickly than work in New York on a comprehensive memorial to the 2,973 victims of the Sept. 11, 2001, attacks. Construction in Manhattan began a year ago; since then, it has been redesigned to trim a construction budget that was approaching $1 billion.

Debate continues about security issues for an underground portion of the memorial, and many family members feel that their loved ones should be listed in a different planned order around the memorial, and with more information next to their names.

The Spanish bombings were claimed by Muslim militants who said they were acting on behalf of Al Qaeda to avenge the presence of Spanish troops in Iraq and Afghanistan. Spanish investigators say, however, that the cell did not receive orders or financing from Usama bin Laden's terrorist group, but was inspired by it. Twenty-nine people are on trial in Madrid over the attacks.

The conservative government in power at the time of the attacks had sent 1,300 peacekeepers to Iraq and initially blamed the Basque separatist group ETA, maintaining this argument even as evidence emerged of the involvement of Islamic extremists.

That led to allegations of a cover-up to divert attention from its unpopular support of the war in Iraq, and in elections three days after the attacks the conservatives were voted out of power. Victorious Socialists led by Jose Luis Rodriguez Zapatero, now the prime minister, quickly brought home Spain's troops from Iraq.

The attacks left Spain deeply divided. Conservatives question the Socialist government's legitimacy, saying it took power through tragedy and unfairly refuses to resume a probe into a possible ETA link. The Socialists say the conservatives made Spain a terror target by backing the war.

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