Spain's acting interior minister says the suspected ringleader behind the March 11 train bombings in Madrid killed himself as police closed in on him. He and others who blew themselves up were preparing to carry out more terrorists attacks.

The four suspected terrorists blew themselves up late Saturday as members of an elite corps of police closed in on their hideout in an apartment house in the south Madrid suburb of Leganes.

One Spanish police agent also was killed and 15 others agents injured when the explosion ripped open one side of the building, exposing three floors.

According to acting Interior Minister Angel Acebes, the suicide of the four suspects meant that the core members of the terrorist cell that organized the bombing of four commuter trains heading for Madrid on March 11 are either dead or in prison.

Mr. Acebes said that among those killed in the Saturday night blast was the suspected leader of the terrorist cell, a Tunisian identified as Sarhane ben Abdelmajid Fakhet.

He and another suspect, a Moroccan named as Agdennabi Kounjaa, were on a list of six suspected terrorists for whom a Spanish judge had issued an international search warrant.

A third suspect was not on that list, while the fourth was not immediately identified.

Authorities said one of the suspects' bodies was found wearing a belt loaded with explosives.

The interior minister said police searching the rubble of the apartment building also found 22 pounds of intact dynamite and 200 detonators of the type used in the Madrid attacks and attached to a bomb found Friday on tracks of the high-speed train that runs between Madrid and Seville.

Mr. Acebes said that the suspects were clearly planning to carry out more terrorist attacks. He also said that two or three other people may have escaped the police dragnet before the blast.

Spain is holding 15 people, 11 of them of Moroccan origin, in connection with the train bombings.

Mr. Acebes has blamed the Madrid bombings on the Moroccan Islamic Combatant Group, which allegedly is linked to Osama bin Laden's al-Qaida terrorist network and to a suicide terrorist attack in Casablanca last May that killed 24 people.