The three-judge panel also cleared another 10 defendants of all charges, CNN reported.

The convictions were largely related to document forgery and membership in a terrorist group -- forming jihadist cells while serving time in prison cells. Most had been arrested after the 2004 Madrid train bombings that killed 191 people.

The judges ruled that while one of the defendants had come up with the idea of bombing the anti-terrorism courthouse in Madrid, the reputed plot had not advanced to the legal level of a conspiracy.