Istanbul, Turkey (CNN) -- The man who shot Pope John Paul II in 1981 was released from prison in Turkey Monday, Turkey's Anadolu news agency reported.

Mehmet Ali Agca, now 52, severely wounded the pontiff in Rome's St. Peter's Square on May 13, 1981. John Paul spent six hours on an operating table and survived.

Four days later he announced from his hospital bed he had forgiven the attempted assassin and urged the faithful to pray for Agca. The pope spent more than three weeks in Gemelli hospital recovering.

Agca was arrested a few minutes after the attack, tried, and sentenced to 19 years in prison.

He has never explained why he tried to kill the pope. There has long been suspicion that he was working for an eastern European Communist government angry at the Polish-born pope's vocal anti-Communism. But on a 2002 visit to Bulgaria -- a focus of much speculation -- the pope said he did not believe the Balkan state was behind the attempt on his life.

The pope visited Agca in prison on December 27, 1983, and reportedly forgave him in person.

Agca was granted clemency by the president of Italy in 2000, to John Paul's "satisfaction," according to the Vatican.

He was then transferred to his native Turkey, where he was re-arrested for the murder of a Turkish journalist in 1979.

Agca killed Abdi Ipekci in 1979, Anadolu said. Ipekci was editor-in-chief of the daily Milliyet.

Agca was due to be taken to a military facility to assess his fitness for military service after his release. In 2006, a military hospital ruled that he was not fit for the obligatory military service due to a severe anti-social personality disorder, but the Ministry of National Defense did not approve the exemption, the Turkish news agency said.