Istanbul's chief prosecutor's office has said that journalist Jamal Khashoggi was suffocated as soon as he entered Saudi Arabia's consulate in a planned killing four weeks ago, and his body was then dismembered and disposed of.
In a statement issued after two days of talks with Saudi Arabia's public prosecutor Sheikh Saud al-Mojeb, it also said no concrete results were reached in those meetings.
Mr Khashoggi's death has escalated into a crisis for Saudi Arabia, the world's top oil exporter, which at first denied any knowledge of or role in his disappearance on 2 October.
Mr Mojeb later said the killing was premeditated and Riyadh said 18 suspects had been arrested.
But Turkey, which released a stream of evidence undermining Saudi Arabia's early denials, has demanded more details including the whereabouts of Mr Khashoggi's body and who ordered his killing.
"Despite our well-intentioned efforts to reveal the truth, no concrete results have come out of those meetings," the Istanbul prosecutor's office said of the talks between Mr Mojeb and Istanbul chief prosecutor Irfan Fidan.
The killing of Mr Khashoggi, a critic of de facto ruler Crown Prince Mohammed bin Salman, has put into focus the West's close relationship with Saudi Arabia - a major arms buyer and lynchpin of the US regional plans to contain Iran.
Turkish President Recep Tayyip Erdogan, who has demanded more information from Saudi Arabia, has said Mr Fidan had asked Mr Mojeb to disclose who sent a 15-strong team from Riyadh which is suspected of involvement in the killing.
The prosecutor's statement said Mr Fidan also repeated Ankara's request for the 18 suspects to be extradited to face trial in Turkey, and asked Mr Mojeb to disclose the identity of a "local cooperator" who, according to a Saudi official, disposed of Mr Khashoggi's body.
In a written response, Mr Mojeb invited Mr Fidan to Saudi Arabia to question the suspects and determine "the fate of the body" and establish whether the killing was premeditated, the Turkish prosecutor's statement said.
It added that Mr Mojeb's response also distanced Riyadh from the idea that a "local cooperator" had been involved, saying that Saudi authorities had not made an official statement to that effect.
Mr Mojeb left Turkey today after a three-day visit during which he also held talks at the offices of Turkey's National Intelligence Agency (MIT).
Turkey's relations with Saudi Arabia were strained last year when Ankara sent troops to the Gulf state of Qatar in a show of support after its Gulf neighbours, including Saudi Arabia, imposed an embargo on Doha.
Mr Erdogan's government has pressed Riyadh to conclude its investigation as soon as possible.
"The whole truth must be revealed," Foreign Minister Mevlut Cavusoglu has said.
Mr Erdogan has also called on Saudi Arabia to disclose who ordered Mr Khashoggi's killing.
"There is no point in procrastinating or trying to save some people from under this," he told reporters yesterday.
