Four people were arrested in the Madrid region on Tuesday on charges of jihadist activity, the Interior Ministry said.
Three are Moroccan nationals, the fourth has Spanish citizenship.
The suspects were detained by Civil Guard officers in Pinto and Ciempozuelos, outside the capital, and accused of leading an organized group that used online tools to recruit people for the Islamist cause.
The suspects exerted great personal control over their targets, telling them how to perform nearly every activity in their everyday lives
Investigators found a stable structure that was being used to publish and distribute propaganda praising jihadist terrorism through web platforms and instant messaging applications.
The members of the group delivered their message to hundreds of people, then selected much smaller groups for a more intense and direct radicalization program.
The suspects exerted great personal control over their targets, telling them how to perform nearly every activity in their everyday lives.
Civil Guard investigators are also searching premises in Pinto, Ciempozuelos and the city of Madrid, in order to learn more about the way the group worked.
The operation is being overseen by the High Court, Spain’s central criminal tribunal.
The Interior Ministry noted that recruiting and indoctrination networks are terrorist groups’ main source of human capital, especially in European countries where secure online communications makes it easy to disseminate propaganda and keep in touch with militants in combat zones. These logistics structures can also be used to prepare attacks on European soil.
Ever since Spain’s alert level was raised to 4 on June 26, 2015, the Civil Guard has ramped up investigations into jihadist propaganda and recruitment structures.
English version by Susana Urra.