Agca, 48, identified as a former right-wing hitman, served nearly two decades in an Italian prison for the May 13, 1981, shooting of the pope in St. Peter's Square before being pardoned in 2000 by Italian President Carlo Azeglio Ciampi.
He was then transferred to Turkey to serve time for other crimes, with his time in the Italian jail counting as time served for those charges, CNN said.
Less than six hours after his release Thursday, Turkish Justice Minister Cemil Cicek said that Agca's case would be reviewed by the Court of Appeal "to make sure that no errors were committed in the complicated case," the Times of London said.
John Paul was shot three times at close range but survived and later publicly forgave Agca.
Notable deaths of 2014 [PHOTOS]