The suspects, identified only as F.S.D. and M.C.S., were detained in Barcelona early Wednesday as part of an ongoing operation.
The two suspects are part of a well-organized, “extremely dangerous” anarchist commando with strong international connections, Interior Minister Jorge Fernandez Diaz said.
“They are very well known for their criminal history in Chile,” he added.
A powerful homemade bomb exploded Oct. 2 in the nave of the Basilica of Our Lady of the Pillar in Zaragoza without causing any injuries, even though the church was open to the public at the time of the blast.
The so-called “Mateu Morral Insurrectional Commando,” named after a Spanish anarchist who in 1906 carried out an assassination attempt against the then-Spanish king, Alfonso XIII, and his wife, Victoria Eugenia, on their wedding day, claimed responsibility for the bomb.
That same anarchist group also claimed responsibility for the planting of an explosive device at Madrid’s Almudena Cathedral in February.
The explosion at the Zaragoza basilica destroyed several of the wooden pews facing the main altar.