Spanish police have arrested some 200 suspected jihadi activists since Spain raised its national security alert to one step below the maximum in 2015.
In an interview with Catalan TV, Josep Lluis Trapero, the commander of the local police, noted the detainees had a "clear membership" of the Islamic State, and that investigation could help find the chief plotters of the terrorist attacks that hit Belgium and France.
Islamic State claimed responsibility for the atrocities at Brussels airport and on a train on the city's subway that killed 32 people and wounded 300 more.
The raids were co-ordinated with Belgian and Moroccan police.
The assaults in March 2016 are thought to have been carried out by some of the same individuals responsible for the Paris attacks the previous November. Those figures did not include the arrests made Tuesday.
TARGET The operation is against radical Islamic terrorism and drugs trafficking
There is no evidence the group planned to carry out attacks in Catalonia or elsewhere in Spain, regional Interior Minister Jordi Jané said, according to Europa Press news agency.
The raids follow an eight-month investigation in which the police observed a group which they said was associated with Islamist militants and had links to organised crime in the Barcelona area.
During the raids police seized guns and drugs, as well as computers and memory drives, which were being analysed.
The nine arrested men were Moroccan apart from one Spaniard and were aged between 30 and 40, the police said.