Spanish authorities have arrested three suspected members of the al-Qaeda terror network who were allegedly planning an attack.

The three detainees, a Russian, a Turk and a Chechen, were picked up in the southern Spanish city of La Linea near Gibraltar and in the central town of Ciudad Real.

Their names were not disclosed.

Police found explosives in the Turk’s house in La Linea –in sufficient quantity to blow up a bus. However, authorities did not reveal what specific targets the suspects were interested in, except to say that "there are clear indications they could have been planning an attack in Spain and/or another country.”

Spain's Interior Minister Jorge Fernandez Diaz told reporters: "This is one of the most important operations carried out against al-Qaeda…. Police moved to arrest them when it became known that they planned to leave Spain.”