Spanish police on Sunday arrested at least six suspects that they say are linked to al Qaeda and "Islamic State" jihadists.

The investigation is ongoing, but Sunday's raids were the culmination of a probe that began in 2014. Police say they have evidence that those arrested provided "logistical support that was essential for the maintenance of terror activities" in Syria and Iraq.

"Four of those arrested are Spanish nationals of Syrian, Jordanian and Moroccan origin," according to a police statement.

One Syrian and one Moroccan suspect were also taken into custody. There were reports of a seventh arrest, but details of the suspect's background were not immediately clear.

Police said they are investigating "foreign structures" of the self-styled "Islamic State," which is alternatively known as ISIL, ISIS or Daesh, and the Al-Nusra Front, an al Qaeda affiliate in Syria.

bik/tj (AP, AFP)