But the Madrid High Court dismissed charges that three defendants killed 2,973 people in the attacks.

Prison sentences were handed down to 18 al-Qaeda suspects in Europe’s biggest trial of Islamic militants. But the court ruled that only Imad Eddin Barakat Yarkas, the leader of the cell, was guilty of conspiracy to murder.

Barakat Yarkas, alias Abu Dahdah, 41, born in Syria but naturalised Spanish, was also found guilty of belonging to a terrorist group and received a 27-year sentence.

He arrived in Madrid in 1982 and recruited Muslim radicals to send to al-Qaeda training camps. He was in contact with Islamic fundamentalists in London, along with Muhammad Atta, the alleged leader of the attacks in New York and Washington in 2001.

Driss Chabli, a Moroccan and an associate of Abu Dahdah, was sentenced to six years for belonging to a terrorist organisation. He is also implicated in suicide bombings in Casablanca in May 2003, and the train bombings in Madrid in March 2004.

Taysir Aloney, a Syrian journalist with the satellite television channel al-Jazeera, who obtained the first television interview with Osama bin Laden after the 9/11 attacks, was found guilty of collaborating with a terrorist organisation and sentenced to seven years. Originally an Arabic translator in Granada for the Spanish state news agency, he used his cover to transfer funds to Afghanistan for Abu Dahdah.

The trial without jury was held in a fortified building in the Casa de Campo park in Madrid.

A 692-page indictment from Baltazar Garzón, the investigative judge, resulted in the arrest of most of the suspects a month after the September 11 attacks. It showed that many of those on trial had been under police surveillance since 1995. Their main activities in Spain included the recruitment of extremists at mosques.

The cell also met and helped at least one of the 9/11 pilots; raised funds by selling drugs and mugging tourists; and liaised with Muslim radicals in London, Paris and Hamburg.

The verdict was expected to provide impetus to Spanish requests for the extradition from London of Farid Hilali, another 9/11 suspect. He spoke by telephone on four occasions from London to Abu Dahdah before and after 9/11.

In a wire-tapped telephone call with the head of the al-Qaeda cell in Madrid, Hilali said: “They are giving very good classes . . . we have entered the area of aviation,” and “We have slit the bird’s throat.”

French anti-terrorist police arrested nine Islamic militants of Algerian origin yesterday who they said were plotting attacks in France. The arrested men are members of the Salafist Group for Preaching and Combat, an Algerian group allied to al-Qaeda and which said in August that it was targeting France. Those arrested include Safe Bourada, an Algerian jailed for ten years in

1998 for taking part in a terror campaign on the Paris Métro that killed nine people in 1995. He was released early in 2003.

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