Two Mossos take off a suspect of Brussels terror attacks in Barcelona. Albert Garcia

The Catalan regional police, the Mossos d’Esquadra, have carried out 12 property searches in Barcelona and in a number of locations in the metropolitan area, including L’Hospitalet de Llobregat, Santa Coloma de Gramenet, Ripollet, Cornellà de Llobregat and Masquefa.

They are youngsters with prior records, several of which are linked to drug trafficking Mossos chief Josep Lluís Trapero

The investigation was prompted eight months ago based on unconnected information supplied by members of the public and due to preventive work carried out by the Mossos. “They have not carried out any actions in Catalonia,” explained Josep Lluís Trapero, the head of the Mossos. “They are youngsters aged between 31 and 39, with prior records, several of which are linked to drug trafficking.”

In an interview with regional channel TV3, Trapero added that the suspects under arrest are Moroccans resident in Catalonia.

The information gleaned as a result of investigations carried out by the Mossos was taken to a High Court, which began a probe and ordered the creation of a joint Spanish-Belgian team under the European Union judicial coordination program known as EUROJUST. Over recent months, the program saw an intensive exchange of information between the Belgian police and the Mossos. The result was evidence pointing to a direct link between the suspects and jihadist terror groups.

A joint Spanish-Belgian team was created under the EU judicial coordination program known as EUROJUST

The scope of the operation saw the Mossos inform Spain’s intelligence services of their findings, which led to a further exchange of information. Also involved were the anti-terrorist branches of the Spanish National Police force, as well as the Belgian Federal Police.

While Spain has not suffered an Islamist-inspired terror attack since the Madrid train bombings in 2004, in recent years there have been regular arrests of suspects thought to have been carrying out recruiting activities for jihadist groups.