Three Spaniards were held in Spain’s north African enclave of Ceuta and a fourth in the Moroccan city of Nador.
A spokesman for Spain’s Interior Ministry said in a statement the arrests were part of a “police operation against jihadist terrorism”.
The statement added: “The arrests have taken place in Ceuta, where three Spaniards have been arrested, and in Nador in Morocco where a Moroccan national has ben held.
“The police investigation has led to the neutralisation of this recruitment and indoctrination cell which specialised in recruiting and sending fighters to join the ranks of ISIS in the Iraq-Syria area, and also to find new recruits to carry out terror attacks in Spain and Morocco.”
The detainees will be flown to Madrid to be quizzed in a private hearing by a judge leading the judicial probe.
Heavily-armed police were maintaining a high presence this morning in several parts of a working-class neighbourhood of Ceuta known as El Principe which is home to an estimated 15,000 Muslims where the arrests are understood to have taken place.
The sprawling area, on a barren hillside called as Monte Chico, is a well-known hotbed of Islamic extremism and provided the setting for a hit crime series on Spanish television.
Most of the terror suspects arrested last year in Spain were held in Ceuta or Spain’s other north African enclave of Melilla.
Last December a 34-year-old Spaniard living in Ceuta was held on suspicion of targeting vulnerable children through a local cultural centre and brainwashing them into wanting to fight for ISIS.