The Spanish government Friday formally began extradition proceedings for suspected Islamic radical Rabei Osman Sayed Ahmed, known as "Mohamed the Egyptian," who was arrested Tuesday in Italy on suspicion of playing a key role in the deadly morning rush-hour train bombings in Madrid exactly three months ago. The Spanish cabinet formally approved the extradition request, as is required by law. An Interior Ministry official said Ahmed would be charged with multiple counts of murder, planning a terrorist act and involvement in a terrorist organization.

In a telephone interview, the official said that Spanish investigators "have yet to receive concrete evidence regarding Mohamed the Egyptian's precise links with the terrorist attacks in Madrid" but added that more information would soon be released by the courts. Following Spanish government practice, the official spoke on condition of anonymity.

Italian officials said Ahmed had been under surveillance for several months and apparently boasted in a series of intercepted phone conversations that he had been involved since 2001 in planning the Madrid attacks. The Italian anti-terror police said they moved quickly to arrest Ahmed and another man in Milan when it became apparent that the men were in the final stages of planning a new attack in Europe.

In one tape-recorded conversation, as depicted in the Spanish and Italian media, Ahmed says: "I am telling you the truth -- the Madrid trail leads to me, even though I was not there when it happened. Before the operation, on the 4th, I had contact with them. But don't you dare tell anyone, I move on my own, while they work in groups."

In another call, Ahmed is reported to have said: "Those martyrs in Madrid were my beloved brothers. That was my project, a project that required a lot of patience and study. It took me two and a half years."

Ahmed is also heard alluding to sending fighters into Iraq, saying, "the first and second groups leave for Iraq on the 20th and 25th of June, by way of Syria." News agencies quoted an Italian prosecutor as saying that U.S. authorities had been provided with a copy of all the transcripts. Though they lack hard evidence, Spanish investigators are working on the theory that Ahmed, a former Egyptian army explosives expert, played a key role in recruiting Sarhane Ben Abdelmajid Fakhet, who authorities contend was the main local operative who carried out the March 11 bombings. Fakhet subsequently died in a fiery suicide explosion along with four others after anti-terror police surrounded their apartment in a suburban Madrid apartment.

Investigators say they believe that Ahmed and Fakhet were together in a house in the suburb Morata de Tajuna where bombs were constructed.

Meanwhile, a Belgian judge ordered four men considered associates of Ahmed to be held for "participation in preparation of a terrorist plot," according to the Belgian attorney general's office, after raids overnight Monday netted 15 suspects. Seven have been released for lack of evidence, and four others were being held for possible immigration violations.

The attacks in Madrid killed what the government now says were 190 people and an unborn fetus and wounded nearly 1,500 others. Just three months later, the makeshift memorial of candles, flowers and handwritten placards at the busy Atocha train station has been removed. The trains are crowded again. But in interviews at the station, many people said the attacks are never far from their minds.

"I tend to be more nervous," said Isabelle Rey, who was waiting with three of her children to board a train Friday on the line that was bombed in March. "I try to look around and see if people are acting suspiciously. I look around for abandoned luggage. Of course, I'm worried for the children."

Daniel Olar, a 19-year-old Romanian immigrant working in Spain laying wood floor panels, said he normally takes the same train that was bombed but happened to be in Barcelona on March 11. He said about 20 of those killed were Romanian migrant workers like him, and he knows of two Romanians who were injured, a woman whose face was half-burned and a man who lost a foot.

Waiting with a friend at the platform at Atocha, he said, "Now I take precautions. I either board the first car or the last car -- never in the middle. The bombs were in the middle."

Special correspondent Maria Gabriella Bonetti contributed to this report.