A Tunisian being sought under an international arrest warrant is the leader of the Madrid train bomb suspects, says Spain's High Court.
Sarhane ben Abdelmajid Fakhet is known as Sarhane 'The Tunisian'
Court papers say Sarhane ben Abdelmajid Fakhet is "the leader and co-ordinator" of people implicated in the attacks.
He is one of six people named as bombing suspects on the international arrest warrant issued by the court.
Meanwhile, security officials say they believe drug-trafficking was key to helping finance the 11 March attacks.
The arrest warrant says Mr Fakhet, alias El Tunecino (The Tunisian), began agitating for a jihad, or holy war, in Madrid from mid-2003, if not before.
A Moroccan, Jamal Ahmidan, is also wanted as a suspected leader of the group.
The four others, Moroccans Said Berraj, Agdennabi Kounjaa and brothers Mohammed and Rachid Oulad Akcha, are wanted after being identified by police as part of the group who placed the rucksack bombs in the trains.
Judge Juan del Olmo, in charge of investigating the attacks, says all are wanted for murder and belonging to a terrorist group.
He also says the bombs were prepared in a house in a semi-rural area outside Madrid, which was rented by one of the suspects.
Thirteen rucksack bombs were left on four packed commuter trains the morning of the 11 March resulting in the death of 191 people and leaving at least 1,800 injured.
Interior Minister Angel Acebes has named the Moroccan Islamic Combatant Group as the main focus of investigation, but he insisted that other "terrorist" organisations had not been ruled out.
The BBC's Katya Adler in Madrid says Spanish security officials now say they believe drug-trafficking played a significant role not only in financing the bombings but also in establishing relationships between key protagonists.
Media reports say Jamal Ahmidan, who has alleged links to al-Qaeda, was orginally recruited by Muslim radicals while serving a prison sentence in Morocco for drug-trafficking.
He is accused of driving a stash of hashish to northern Spain at the end of February to exchange it for 240 pounds of explosives stolen from a mine there.
Spaniard Jose Emilio Suarez Trashorras, now in custody, is accused of supplying the explosives. He also faces multiple counts of murder, as well as attempted murder, robbery and terrorism charges.
Spanish police have 19 people in custody, including 11 Moroccans or Moroccan-born Spaniards, two Indians, two Spaniards and three Syrians.
Fourteen of the suspects have been provisionally charged with mass murder or collaborating with or belonging to a terrorist group.
The Oulad Akcha brothers on the arrest warrant are reported to be related to the only woman charged in the case, Naima Oulad Akcha. Some of the other men have the same surnames as other suspects in custody or who have been questioned by investigators.