As well as having terror links, the suspects also allegedly participated in theft, drug trafficking and other crimes, according to the Mossos d'Esquadra regional police. More than 100 agents took part in the operation, which was ongoing as of mid-afternoon, a spokeswoman said.
The spokeswoman said six venues had been searched in and near Barcelona, the regional capital. She declined to be identified by name in line with the police force's standard practices. Catalan regional minister of security, Miquel Buch, told reporters most of the arrests took place in a central Barcelona neighborhood, but some were made in the nearby town of Igualada.
The five suspected of being part of an extremist cell were originally from Algeria, Buch told reporters. "They were determined about carrying out an attack, but they didn't have the capacity for it," he said.
Investigating magistrate Manuel Garcia-Castellon of the National Court, which normally handles terror-related probes in Spain, ordered the arrests and will be interrogating those who remain in custody later this week, a court spokesman told The Associated Press, following customary rules of anonymity.
Also Tuesday, authorities in southern Spain's Malaga arrested a 27-year-old Moroccan national who police said they suspect could be linked to the Islamic State group. The man allegedly used several social network profiles to express violent views and allegiance to the extremist group.