MADRID, Spain (CNN) -- Spanish police arrested 12 people Thursday on suspicion of Islamic terrorist activities, authorities said.
Eight of them, all Moroccans, were arrested early Thursday. They are suspected of providing cover for five fugitives from the Madrid train bombings four years ago and also of involvement in financing and recruiting of Islamic terrorists, according to the ministry statement and a judicial source.
Later Thursday, police arrested four more people -- three Moroccans and an Algerian -- in their prison cells for similar charges. Additional details about those four were not immediately released.
The operation was conducted on orders of Judge Baltasar Garzon, an investigating magistrate at Spain's National Court, which handles cases of terrorism.
The suspects range in age from 23 to 56. Four are from Tangiers, just across the Mediterranean from mainland Spain, and the others from elsewhere in Morocco, the ministry said.
The Madrid train bombing took place on March 11, 2004, killed 191 people and wounded 1,800.
In the days and months that followed, police arrested a number of suspects in and around Madrid, but determined that a small number of suspects had escaped.
Authorities have long suspected that they had help getting out of the area with the assistance of a secretive group of accomplices.
The main Madrid train bombing trail ended in 2007 with the convictions of 23 men. Five of them were later acquitted by the Supreme Court. A small number of other suspects have yet to stand trial.
Since the bombings, Spanish police have arrested dozens of Islamic terror suspects, who are accused of activities ranging from plotting attacks to providing financing to recruitment.