Saudi journalist Jamal Khashoggi was strangled as soon as he entered the Saudi Consulate in Istanbul as part of a premeditated killing, and his body was dismembered before being disposed of, a top Turkish prosecutor said on Wednesday.Chief Istanbul prosecutor Irfan Fidan's office also said in a statement that discussions with Saudi chief prosecutor Saud al-Mojeb yielded no "concrete results" despite Turkey's "good intentions to uncover the truth".The statement was the first public confirmation by a Turkish official that Khashoggi was strangled and dismembered after he entered the Saudi Consulate on October 2 to collect paperwork he needed to marry his Turkish fiancee."In accordance with plans made in advance, the victim, Jamal Khashoggi, was strangled and killed immediately after entering the Consulate General of Saudi Arabia," the prosecutor's office said.READ: Jamal Khashoggi's fiancée: Why I declined Trump's invitation"The victim Jamal Khashoggi's body was dismembered and destroyed following his death by suffocation again, in line with the advance plans," the two-page statement read.Turkey is seeking the extradition of 18 suspects in the journalist's slaying who were detained in Saudi Arabia. It also is pressing Saudi Arabia for information about who ordered Khashoggi's killing and the location of his remains.Turkish President Recep Tayyip Erdogan has called on Riyadh to disclose the identity of an alleged local collaborator said to have been involved in getting rid of Khashoggi's body.Saudi chief prosecutor al-Mojeb held talks with Fidan and other Turkish officials in Istanbul this week and departed on Wednesday. Saudi Arabia has not commented directly on the prosecutor's visit.Fidan's office said the Saudi delegation submitted a written response to questions and invited the Turkish delegation to come to Saudi Arabia bringing "evidence obtained during the course of the investigation".READ: Turkey wants 18 Saudis extradited over Khashoggi murderThe Saudi representatives said the whereabouts of Khashoggi's remains and whether the killing was premeditated or not would only come to light through a joint interrogation by Turkish and Saudi investigators, according to the statement.The statement said Turkey renewed its request for the 18 suspects to be extradited. It did not say if Turkish officials would travel to Saudi Arabia.Khashoggi, a 59-year-old columnist for The Washington Post, vanished after entering the consulate in Istanbul to pick up paperwork for his upcoming marriage. His fiancee was waiting for him outside. A critic of the Saudi crown prince, Khashoggi had been living in exile in the United States.Turkey alleges a Saudi hit squad from Saudi Arabia — including a member of Saudi Crown Prince Mohammed bin Salman's entourage during a trip to the United States— went to Istanbul to kill the journalist and then tried to cover it up.Under mounting pressure, Saudi Arabia changed its narrative about Khashoggi's killing several times, eventually admitting Khashoggi died inside the consulate. Saudi Arabia only recently acknowledged Turkish evidence showed the slaying was premeditated.