Spanish authorities say they have arrested three suspected members of al-Qaida.

Spanish Interior Minister Jorge Fernandez Diaz told reporters Thursday that there was a “clear indication” that those detained could have been planning an attack in Spain or Europe.

Authorities accuse the men of storing explosives that the minister said would be especially damaging with shrapnel and could even destroy an entire bus.

Officials describe the suspects as being from the Caucasus region — possibly Chechens and one Turkish man. Police arrested the two Caucasians in Spain's autonomous community of Castile-La Mancha and arrested the Turkish suspect in La Linea de la Concepcion, where the trio allegedly was storing the explosives in an apartment.

Spanish news reports say police suspect at least one of those arrested had attended militant training camps in Pakistan.