Mehmet Ali Agca, the man who shot Pope John Paul II in 1981, has been detained and is set to return to jail after Turkey's Supreme Court today overturned a decision to release him.
Following the ruling, security forces seized Agca from an address in Istanbul and took him to police headquarters, Istanbul Governor Muammer Guler said on the NTV news channel.
The Justice Ministry had appealed against the move to release Agca from prison last week after he had served more than 25 years behind bars in Italy and Turkey.
The 48-year-old former right-wing gangster had served 19 years in an Italian prison for the assassination attempt before being pardoned at the Pope's behest in 2000.
He was then extradited to Turkey to serve a separate sentence in an Istanbul jail for the 1979 murder of liberal newspaper editor Abdi Ipekci and charges dating from the 1970s.
Under new Turkish laws, his time served in Italy was initially deducted from the 25 years left on his sentence in Turkey.
But the Supreme Court ruled against this.
"There is no legal foundation for deducting Agca's time spent in prison in Italy from the punishments for crimes which he committed in Turkey," the court said in a written statement.
The chief prosecutor, who had the sole authority to challenge the verdict, did not do so and the ruling was sent to the lower court dealing with Agca's case.
The lower court must now calculate how much more time he should serve in prison.
In the first government comment on the ruling, Prime Minister Tayyip Erdogan said: "The justice ministry did its duty. After this it is down to the legal process."