The plane arrived at Istanbul airport on Tuesday night.

This is a dream - I cannot believe it

Mehmet Ali-Agca

In Turkey he must serve the remaining nine years of a 10-year sentence he received for killing a newspaper editor, Abdi Ipekci, in 1978.

Clemency

Chief Vatican spokesman Joaquin Navarro-Valls described the Pope as "very happy" about the pardon.

"He [the Pope] has been insisting on this for some time. We are not surprised," the spokesman said.

He added that that "the Pope's satisfaction was even greater" because the clemency was granted during the Roman Catholic Church's Holy Year, the theme of which is pardon and forgiveness.

The Pope narrowly escaped with his life

The attempt on the Pope's life - on 13 May 1981, less than three years after his accession to the Papacy - came as he drove across Saint Peter's Square in an open car to hold a general audience with a crowd of 20,000 people.

He was hit by three bullets - one entered his stomach, another hit his left hand and the third his right arm.

Two of his aides were also injured in the attack. Mr Agca was arrested by Italian police as he tried to flee the scene and he was sentenced to life imprisonment.

Mystery

The Pope later publicly forgave Mr Agca and even visited him in prison. The Vatican had said it would not stand in the way of Italian justice in the case.

Despite three investigations and two trials, mystery has long surrounded the assassination attempt.

It was at first believed to be linked to Bulgarian and Soviet secret services as part of a communist plot to kill the Pope, who helped to loosen the grip of communist authorities in his Polish homeland.

However, at the second trial in 1986, prosecutors failed to prove charges that Bulgarian secret services had hired Mr Agca on behalf of the Soviet Union.

In April 1980, a court martial in Istanbul sentenced him in absentia to death for his part in the Ipekci assasination.

This was later commuted to a 10 year jail term following an amendment to Turkish laws.