Mehmet Ali Agca went back to jail on Friday

Last week Turkey's top court had ruled that Mehmet Ali Agca had not spent enough time in jail for killing a Turkish journalist in 1979.

He was released earlier this month, but was returned to jail after eight days.

He has spent nearly 25 years in Italian and Turkish jails but has never revealed why he tried to kill the Pope.

Prosecutors say Agca, 48, must now stay in prison until 18 January 2010, the Anatolia agency reports.

Turkish Justice Minister Cemil Cicek had appealed against his release earlier this month, arguing that cuts in his original jail term had been miscalculated.

Mr Cicek said Agca should serve a full 10-year term for the 1979 murder of left-wing Turkish journalist Abdi Ipekci, as well as two bank robberies.

Mystery motive

While awaiting trial for the murder of Ipekci, Agca escaped from prison, re-appearing in Rome to shoot at the Pope.

Press outrage at release On this day: Pope shot Mysteries linger over attack

The critically wounded pontiff underwent emergency surgery for serious wounds to the abdomen and hand. According to his own account, he only just survived.

The Pope met his attacker two years later in an Italian prison, when he publicly forgave him.

There were claims that the Soviet KGB and its Bulgarian counterpart were behind the assassination attempt, but prosecutors at a trial in 1986 failed to prove a link to the Bulgarian secret service.

On a 2002 visit to Sofia, John Paul II said he had never believed in a Bulgarian link to the shooting.

The Russians have always maintained that the KGB was not responsible, even indirectly, for the attempt on the pontiff's life.