The Interior Ministry identified Jamal Ahmidan as the "brains" behind the 11 March train bombings that killed 191 people.
One other alleged ringleader is believed to have been among the suspects who blew themselves up when their suburban Madrid apartment was surrounded by police.
Also today, Spanish police said they arrested two more suspects on 3 April, one in a Madrid suburb and the other in Ceuta, a Spanish exclave on the Moroccan coast.
Over the weekend, a group claiming responsibility for the bombings sent a letter to a Spanish newspaper threatening to turn the country into an "inferno" if it does not halt its support for the United States and pull its forces out of Iraq and Afghanistan.
A government spokesman said today the fax has some credibility.
One other alleged ringleader is believed to have been among the suspects who blew themselves up when their suburban Madrid apartment was surrounded by police.
Also today, Spanish police said they arrested two more suspects on 3 April, one in a Madrid suburb and the other in Ceuta, a Spanish exclave on the Moroccan coast.
Over the weekend, a group claiming responsibility for the bombings sent a letter to a Spanish newspaper threatening to turn the country into an "inferno" if it does not halt its support for the United States and pull its forces out of Iraq and Afghanistan.
A government spokesman said today the fax has some credibility.