Saudi chief prosecutor al-Mojeb met with Fidan twice and also visited the Turkish intelligence agency's Istanbul headquarters this week before leaving for Riyadh on a private jet Wednesday.
Under mounting pressure, Saudi Arabia changed its narrative about the killing several times, eventually admitting that Mr Khashoggi died inside the consulate and only recently acknowledging that Turkish evidence shows his killing was premeditated.
He flew out of Istanbul this afternoon without making a public statement.
Turkey's relations with Saudi Arabia were strained previous 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.
Turkish authorities said they were not satisfied after the talks with the Saudi prosecutor.
The statement follows weeks of media reports about the murder at the Saudi consulate in Istanbul on 2 October.
It said 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.
US Defence Secretary Jim Mattis said Sunday that Al Jubeir assured him that Riyadh would conduct a "full" investigation, adding he was confident the probe would include Turkey's findings. Pompeo in his call for urgent movement toward a political solution to the fighting.
The case has also sorely strained relations between the ultra-conservative kingdom and the West.
Turkey alleges a hit squad from Saudi Arabia travelled to Istanbul to kill the journalist and then tried to cover it up.
"This crime has to be punished and the perpetrators identified".
"The whole truth must be revealed", he said.
In an editorial published yesterday, the Washington Post accused Riyadh of "deflecting questions by pretending to investigate" the murder.
The death of Khashoggi - a Washington Post columnist and a critic of Saudi Arabia's de facto ruler, Crown Prince Mohammed bin Salman - sparked global outrage and pitched the world's top oil exporter into crisis.
VOA reported last week about a series of Khashoggi-related discussions involving princes sidelined by MBS and who bear the crown prince a grudge.
Even before Khashoggi's murder, there had been talk in Saudi expatriate circles that Ahmad was ready to become outspoken in criticism of MBS's policies, especially over the war in Yemen and his eschewing of traditional rule-by-family-consensus.
The worldwide community refused to accept the Saudi claim that the incident was not a premeditated murder.
"We therefore request that you suspend any related negotiations for a U.S. -Saudi civil nuclear agreement for the foreseeable future", said the lawmakers, who included senators Cory Gardner, Rand Paul, Dean Heller and Todd Young.