Spain and Morocco have arrested 14 people in a joint operation targeting suspected recruiters for the so-called Islamic State (IS) group, the reports.
The arrests were made in suburbs of Madrid and in various Moroccan cities.
Those arrested are suspected of involvement in a network to send fighters to areas of Syria and Iraq under IS control.
On Friday a Moroccan who had lived in Spain was arrested following a foiled attack on a high-speed French train.
Ayoub El-Khazzani, 25, originally from Tetouan in northern Morocco, arrived in Spain in 2007 and lived there for seven years, in Madrid and Algeciras, before moving to France.
He is suspected of having had contact with radical Islamists and had been put on a list marked as “potentially dangerous” by Spanish authorities. They flagged this up to French counterparts in February 2014.
Spanish counter-terrorism sources quoted on Monday by the Spanish Cadena Ser radio network said that some 800 people with a radical Islamist profile were in Europe and ready to strike, having returned from Syria and Iraq.
The latest arrests took place in the San Martin de la Vega district of Madrid, and in the Moroccan cities of Fez, Casablanca, Nador, al-Hoceima and Driouech.
The Spanish interior ministry said the operation was ongoing, without giving specific details.
Both Spain and Morocco have arrested dozens of suspected radical Islamists in recent years.
Islamic State fighters have overrun large parts of Syria and Iraq si