Moutaz Almallah Dabas wanted in Spain for alleged involvement in the Madrid train bombings faces extradition from Britain.
Dabas, 39, was arrested in Slough, west of London, in March. An extradition warrant issued by Spain alleges that Dabas helped manage a group of radical Islamists that included some of the Madrid bombers.
District Judge Anthony Evans ordered that Dabas remain in custody until a further hearing on Sept. 28. He didn't rule on Spain's extradition request.
Dabas, who was born in Syria and holds Spanish citizenship, attended the hearing at Bow Street Magistrates' Court but spoke only to confirm his name, the AP reports.
Lawyers acting for the Spanish authorities have previously alleged that Dabas helped indoctrinate Islamic militants in Spain.
"He kept in his house texts authored by or distributed by Osama bin Laden and he stated his affinity to the jihadist thesis of Osama bin Laden and al-Qaida," lawyer John Hardy told an earlier hearing.